Try:
1.Rb5~ ?
but 1.... Kf1-e1!
1.Rb5-b3? threat:
2.Rb3-e3 Kf1-e1
3.Qa1-a5+ Ke1-f1
4.Ba6*e2+ Bd1*e2
5.Re3-f3+ Be2*f3 #
but 1.... Kf1-e1!
[1.Qa1*d1+? but 1....Re2-e1!]
Solution:
1.Rb5-b2!
1...Kf1-e1
2.Rb2*e2 + Ke1-f1
3.Sg4-h6 g5-g4
4.e4-e5 g4-g3
5.Re2-e4 + Kf1-f2
6.Qa1*d1 g3-g2 #