Key: 1.Qb8! Bxb8 2.Sg5+ Ke5 3.Sxf7+ Ke4 4.Sg5+ Ke5/f5 5.Sxh3+ (2…Kf5 3.Sxh3+ Ke4 4.Sg5+ Ke5/f5 5.Sxf7+) 5…Ke4 6.Sg5+ Ke5/f5 7.Sh7+ Ke4 8.Sf6# 7…Kg4 8.Rg5#
Doubled knight Zwickmühle with an added Queen sacrificial key. The order in which white must take on h3 and f7 is forced and reversed in each variation.
