a) diagram
1.Sbc4? zugzwang.
1...Kd3 (a) 2.Qf3+ Kc2 3.Qb3+ Kc1 4.Qb1# 2...Kd4 3.Qa3 zz. Kd5 4.Qd6#
but 1...Kc3! (b)
1.Qe2? (A) zugzwang.
1...Kc3 (b) 2.Sdc4 (B) [ th. 3.Qd2+ Kb3 4.Qb2# ] 2...Kb4 3.Qe5 zz. Kb3 4.Qb2#
but 1...Kc5!
1.Sdc4! (B) [ threat: 2.Qd5+ Kc3 3.Qd2+ Kb3 4.Qb2# ]
1...Kc3 (b) 2.Qe2 (A) [ th. 3.Qd2+ Kb3 4.Qb2# ] 2...Kb4 3.Qe5 zz. Kb3 4.Qb2#
1…Ke4 (d) 2.Qd5+ Kf4 3.Qe5+ Kf3 4.Qe3#
b) wSb6→c5
1.Sce4! zugzwang.
1...Kd3 (a) 2.Qf3+ Kc2 3.Qb3+ Kc1 4.Qb1# 2...Kd4 3.Qg3 zz. Kd5 4.Qd6#
1...Ke3 (c) 2.Qf3+ Kd4 3.Qg3 zz. Kd5 4.Qd6#
c) wQh5→h6
1.Sbc4! zugzwang.
1...Kd3 (a) 2.Qe3+ Kc2 3.Qb3+ Kc1 4.Qb1#
1...Kc3 (b) 2.Qe3+ Kb4 3.Qe5 Ka4 4.Qa5# 2...Kc2 3.Qb3+ Kc1 4.Qb1#
[ 1...Kc5 2.Qb6+ Kd5 3.Qd6#, 1...Kd5 2.Qd6# ]
