The answer is for black to play K-f4. White is forced to play g5. Black then plays K-f5 and white has only one move which is g6 and black checkmates with hxg6.
I hope you found the answer. Look for another new challenging chess strategy puzzle in my next post! If you would like to have these puzzles sent to you, just add your email address in the “Subscription Options” box and click “Subscribe.”