1. Bh4 g1 (Q,B,R)
1. ... h1 (Q,R)
3.Kg3 ... (Q,R is going nowhere good, white wins)
1. ... Kg1
i suppose white's passed pawns mean underpromotions will lose for black so long as g3 is held by king. but then i'm too lazy today to think it through, and it's taken 5 edits already
edit6: 1... Kg1, 2. Kg3 h1(B) looks drawn. perhaps i'm on the wrong line altogether. g'night.