The Windows at R2C2, R2C6, R6C2 and R6C6 are numbered W1, W2, W3 and W4
In the following walkthrough I’ve used Windoku properties, the four given windows and five hidden ones, as in my post in the Standard Techniques forum
here.
I’ve started by using steps from my version A walkthrough, modified where necessary because of the removal of the cage R56C1.
Prelims
a) R12C3 = {69/78}
b) R3C89 = {69/78}
c) R8C67 = {15/24}
d) R9C56 = {59/68}
e) 9(3) cage at R1C6 = {126/135/234}, no 7,8,9
f) 9(3) cage at R6C9 = {126/135/234}, no 7,8,9
g) 9(3) cage at R9C2 = {126/135/234}, no 7,8,9
h) 12(4) disjoint cage at R1C1 = {1236/1245}, no 7,8,9
i) 13(4) disjoint cage at R2C2 = {1237/1246/1345}, no 8,9
1. 12(4) disjoint cage at R1C1 = {1236/1245}, CPE no 1,2 in R5C5 using both diagonals
2. 7 in R9 only in R9C78, locked for N9 and hidden window R159C678, no 7 in R5C678
2a. Hidden killer pair 8,9 in R9C56 and R9C78 for R9, R9C56 contains one of 8,9 -> R9C78 must contain one of 8,9 -> R9C78 = {789}
3. 12(4) disjoint cage at R1C1 and 13(4) disjoint cage at R2C2 both contain 1, each of these cages must have 1 on one of the diagonals -> no other 1 on the diagonals
4. 45 rule on both diagonals 6 innies R4C4 + R5C5 (twice) + R6C6 + R4C6 + R6C4 = 44 can only be 5 + 6 + 7 + 8 + 9 (twice) -> R5C5 = 9, placed for both diagonals, R46C46 = {5678}, locked for N5, clean-up: no 5 in R9C6
5. 9 in hidden window R678C159 only in R678C1, locked for C1
6. 12(4) disjoint cage at R1C1 must have one of 1,2 in R1 and one of 1,2 in R9 (1,2 cannot be in the same row, because they would clash with 9(3) cage at R1C6 or 9(3) cage at R9C2)
6a. 9(3) cage at R1C6 = {135/234} (cannot be {126} which clashes with 1 or 2 in R1C19), no 6, 3 locked for R1 and hidden window R159C678, no 3 in R5C678
6b. Killer pair 1,2 in R1C19 and 9(3) cage, locked for R1
6c. 9(3) cage at R9C2 = {135/234} (cannot be {126} which clashes with 1 or 2 in R9C19), no 6, 3 locked for R9 and hidden window R159C234, no 3 in R5C234
6d. 3 in N5 only in R46C5, locked for C5
7. 12(4) disjoint cage at R1C1 = {1245} (only remaining combination), no 6
7a. 12(4) disjoint cage at R1C1 = {1245}, locked for hidden window R159C159, no 1,2,4,5 in R19C5 + R5C19, clean-up: no 9 in R9C6
7b. R1C2345 = {6789} (hidden quad in R1)
[Thanks HATMAN for pointing out that I’d missed step 7a in my walkthrough for version A.]
8. Naked pair {68} in R9C56, locked for R9 and N8
8a. Naked pair {79} in R9C78, locked for N9
9. 8 in N9 only in R7C78, locked for R7 and W4, no 8 in R6C678
10. 8 in hidden window R678C159 only in R68C1, locked for C1
11. R4C4 + R6C6 + R4C6 + R6C4 contains 8 for one of the diagonals -> 21(4) disjoint cage at R3C3 must contain 8 for the other diagonal = {2478/2568/3468}
11a. Double hidden killer pair 6,7 in R4C4 + R6C6 + R4C6 + R6C4, 21(4) disjoint cage and 13(4) disjoint cage at R2C2 for both diagonals, R4C4 + R6C6 + R4C6 + R6C4 contains both of 6,7, 21(4) disjoint cage contains one of 6,7 -> 13(4) disjoint cage must contain one of 6,7 -> 13(4) disjoint cage = {1237/1246}, no 5
11b. 12(4) disjoint cage at R1C1 and 13(4) disjoint cage at R2C2 both contain 2, each of these cages must have 2 on one of the diagonals -> no other 2 on the diagonals
11c. 21(4) disjoint cage = {3468} (only remaining combination), no 5,7
11d. 21(4) disjoint cage contains 6 -> 13(4) disjoint cage must contain 7 = {1237}, no 4,6
12. 14(3) cage at R2C1 = {167/257/347/356}, R5C1 = {367} -> combined cage 14(3) + R5C1 = {167}[3]/{257}[3or6]/{347}[6]/{356}[7], 7 locked for C1
12a. 7 in N7 only in R7C2 + R8C23, locked for W3, no 7 in R6C234 + R78C4
13. 7 in hidden window R678C159 only in R78C5, locked for C5 and N8
13a. Naked pair {68} in R19C5, locked for C5
13b. 7 in R1 only in R1C234, locked for hidden window R159C234, no 7 in R5C23
14. R5C19 = {37} (hidden pair in R5)
14a. 14(3) cage at R2C1 (step 12) = {167/257/356} (cannot be {347} which clashes with R5C1), no 4
14b. Killer pair 3,7 in 14(3) cage and R5C1, locked for C1
15. 12(4) disjoint cage at R1C1 = {1245}
15a. Hidden killer pair 2,5 in R1249C9 and 9(3) cage at R6C9, 9(3) cage contains one of 2,5 -> R1249C9 must contain one of 2,5
15b. R1249C9 contains one of 2,5 -> R19C1 must contain at least one of 2,5
15c. 14(3) cage at R2C1 (step 14a) = {167/356} (cannot be {257} which clashes with R19C1), no 2, 6 locked for C1 and hidden window R234C159, no 6 in R234C9, clean-up: no 9 in R3C8
16. 6 in C9 only in 9(3) cage at R6C9 = {126}, locked for C9 and hidden window R678C159, no 1,2 in R678C15
16a. Naked pair {45} in R19C9, locked for C9 and 12(4) disjoint cage at R1C1, no 4,5 in R19C1
16b. Naked pair {12} in R19C1, locked for C1
17. 14(3) cage at R2C1 (step 15c) = {356} (only remaining combination), locked for C1 -> R5C1 = 7, R5C9 = 3
18. Naked triple {356} in 14(3) cage at R2C1, locked for hidden window R234C159, no 3,5 in R234C5
18a. Naked triple {124} in R234C5, locked for C5 -> R6C5 = 3
18b. Naked pair {57} in R78C5, locked for N8, clean-up: no 1 in R8C7
19. 9 in N8 only in R7C46 + R8C4, CPE no 9 in R7C2 using W3
20. 4 in N1 only in R3C23, locked for R3 and W1, no 4 in R2C4 + R4C23
21. 6 in N7 only in R7C23 + R8C3, locked for W3, no 6 in R6C234
22. 3 in N9 only in R7C78 + R8C8, locked for W4, no 3 in R7C6
22a. 3 in N8 only in R789C4, locked for C4
[This is how far I could go using (modified) steps from version A. The placement in R6C1 was very helpful in that version.]
23. 5 in N9 only in R7C8 + R8C7 + R9C9, CPE no 5 in R6C6 using W4 and D\
24. 6 in N3 only in R2C7 + R3C78, locked for W2, no 6 in R234C6 + R4C78
24a. 6 in N5 only in R4C4 + R6C6, locked for D\
25. Consider placement for 5 in C6
5 in R1C6 => R2C7 = 5 (hidden single in N3), locked for W2, no 5 in R4C78
or 5 in R234C6, locked for W2, no 5 in R2C7 + R4C78
-> no 5 in R4C78
26. Consider placement for 4 in N9
4 in R7C78 + R8C7, locked for W4, no 4 in R6C78 + R78C6
or 4 in R9C9 => R7C3 = 4 (hidden single on D/)
-> no 4 in R7C6
[I ought to have spotted this one immediately after step 24a]
27. Consider the placement for 6 on D/
6 in R3C7 => R3C89 = {78}, locked for R3 => no 8 in R3C3
or 6 in R7C7 => R12C3 = {78}, locked for C3 => no 8 in R3C3
-> no 8 in R3C3
27a. 21(4) disjoint cage at R3C3 = {3468}, 8 locked for C7
[Just realised that there’s a step fairly similar to a breakthrough step I used for version A.]
28. Consider values in R5C6
R5C6 = 1
or R5C6 = {24} => 9(3) cage at R9C2 (step 6c) = {135} (cannot be {234} which clashes with R5C6 using hidden window R159C678), locked for hidden window R159C678, no 1 in R5C678
-> no 1 in R5C78
28a. Similarly consider values in R5C4
R5C4 = 1
or R5C4 = {24} => 9(3) cage at R9C2 (step 6c) = {135} (cannot be {234} which clashes with R5C4 using hidden window R159C234), locked for hidden window R159C234, no 1 in R5C234
-> no 1 in R5C23
28b. 1 in R5 only in R5C46, locked for N5
28c. 1 in C5 only in R23C5, locked for N2
29. Consider values in R7C6
R7C6 = 1 => R8C67 = {24}, locked for R8 and W4 => R8C8 = 3
or R7C6 = 2 => R8C67 = [15] => R8C8 = 3
or R7C6 = 9 => R7C1 = 4 => R1C9 = 4 (hidden single on D/) => R9C9 = 5 => R8C67 = {24}, locked for R8 and W4
-> no 2 in R6C78 + R78C8
29a. 2 in R7C6 + R8C67, CPE no 2 in R8C4
[These values in R7C6 can be taken a bit further
R7C6 = {12}, naked triple {124} in R578C6, locked for C6
or R7C6 = 9 => R7C1 = 4 => R1C9 = 4 (hidden single on D/)
-> no 4 in R1C6
4 in R1 only in R1C789, locked for N3
However the next step makes this unnecessary.]
[In feedback about my walkthrough for version A, HATMAN commented that R1C19 and R9C19 must each total 6, after the 12(4) disjoint cage at R1C1 has been reduced to {1245}.]
30. R1C19 and R9C19 must be [15/24] (because [14/25] would clash with 9(3) cages at R1C6 and R9C2) -> R1C1 + R9C9 and R1C9 + R9C1 must be [14/25]
30a. R1C1 + R9C9 = [25] (cannot be [14] which clashes with R3C3 + R8C8, ALS block on D\) -> R1C1 = 2, R9C9 = 5, placed for D\, R1C9 = 4, R9C1 = 1, both placed for D/, clean-up: no 1 in R8C6
30b. 1 in R1 only in R1C78, locked for N3
[Cracked.]
31. Naked pair {24} in R8C67, locked for R8 and W4, no 2,4 in R6C78 + R7C678
31a. R2C8 = 2 (hidden single on D/), placed for W2, no 2 in R2C6
31b. R3C3 = 4 (hidden single on D\)
31c. R8C7 = 4 (hidden single in N9), R8C6 = 2
31d. R7C9 = 2 (hidden single in N9)
32. 5 in W4 only in R6C78, locked for R6 and N6 -> R6C4 = 8, placed for D/
32a. Naked pair {36} in R3C7 + R7C3, locked for D/ and 21(4) disjoint cage at R3C3 -> R7C7 = 8, R8C2 = 7, placed for D/, R78C5 = [75], R4C6 = 5, R1C6 = 3
32b. R4C6 = 5, placed for W2, no 5 in R2C7
33. Naked triple {234} in 9(3) cage at R9C2, locked for hidden window R159C234 -> R5C4 = 1, R5C6 = 4, R4C5 = 2, R23C5 = [41]
34. Naked triple {349} in R789C4, locked for C4 and N8 -> R7C6 = 1
34a. Naked triple {67} in R15C4, locked for C4 -> R2C4 = 5, R3C4 = 2
35. R7C2 = 5 (hidden single in N7), R5C3 = 5 (hidden single in N4), R5C7 = 2 (hidden single in R5)
36. R8C1 = 8 (hidden single in C1)
36a. 9 in R8 only in R8C34, locked for W3, no 9 in R6C23 + R7C4
36b. R8C4 = 9 (hidden single in N8)
37. Naked pair {36} in R78C3, locked for C3, N7 and W3 -> R7C4 = 4, R67C1 = [49], 9(3) cage at R9C2 = [423], R6C23 = [21], clean-up: no 9 in R12C3
38. R6C9 = 6, R8C9 = 1, R8C8 = 3, placed for D\, R2C2 = 1, R57C8 = [86], R3C8 = 7, R3C9 = 8, R7C3 = 3, placed for D/, R3C7 = 6
and the rest is naked singles, without using diagonals or windows.