I can't find it through Rxf4, there's too many shenanigans black can pull.

Going back to the beginning, black's K is trapped. The Q is blocking all of the fun, it needs to go. Promoting the pawn looks tempting but that alone is 2 moves, and can't see the d8 bishop doing anything. I don't think it's either of the rooks, and the pawns are all useless. What's left? The a8 bishop? Hrm.

I think we need to get rid of the black Q and kill with the h4 rook. No idea how though.