Black attack
quicker (unless I have overlooked something)
1 ..., Qc3
2 Kb2, Ra3!
if 3 b2xR, bxa3, 4 Kc1, a2, 5 anything, a1-Q#
if 3 Kc1, Rc - a8, etc... #
if 3 bxQ, bxc3, 4 Kc1, Ra1#, or 4 anything else, Rc-b8+, 5 Kc1, Ra1#
quicker (unless I have overlooked something)
1 ..., Qc3
2 Kb2, Ra3!
if 3 b2xR, bxa3, 4 Kc1, a2, 5 anything, a1-Q#
if 3 Kc1, Rc - a8, etc... #
if 3 bxQ, bxc3, 4 Kc1, Ra1#, or 4 anything else, Rc-b8+, 5 Kc1, Ra1#