Solution
1.+B1c 2.Kx1c 3.B*3a 4.K1b 5.B2b+
1.+B1c 2.Kx1c 3.B*3a 4.K1b 5.B2b+
1.P*2d
there is no way for White to prevent P2c+ on the next move.
1.P*3c
if 2.Bx3c, 3.Rx2a+. if 2.Gx3c, 3.P*2c
1.G*2b 2.Sx2b 3.G*4b
1.+B3a 2.Sx3a 3.N*3c
1.B*4e
1.B4e threatens Bx6c+ and Bx2c+
1.G6h
the Promoted Bishop is trapped.
1.+R2b 2.Kx2b 3.G*2c 4.K2a 5.P*2b 6.K3a 7.G3b
1.B1c+ 2.Kx1c 3.R*1d
1.P*7c
if 2.Sx7c, 3.Rx8c+. if 2.Nx7c, 3.P*7d