White to play and either win black's queen or to mate black's king
Here white has to either win black's queen or to mate black's king.
If black doesn't want to lose his queen, then black will be mated in 3 moves!
For the hint and the answer, look at the bottom of puzzle.
Hint: White wants to mate black's king by playing Qxh7# but white can't do that right now because black's knight on f6 is protecting the h7 pawn. How does white get rid of black's knight?
Answer: 1.Nd5!! see next diagram:
White is now attacking black's queen on c7 and attacking the knight on f6.
If black retreats their queen, for example 1...Qd8, then white plays 2.Nxf6+ Qxf6 (If 2...gxf6 then 3.Qxh7# and if 2...Kh8 then also 3.Qxh7#) 3.Qxh7#.
If black takes white's knight by playing 1...Nxd5 then black's knight is no longer protecting the h7 pawn so now white can play 2.Qxh7#.
If black stops white from attacking the h7 pawn by for example 1...g6, then white simply takes black's queen by playing 2.Nxc7 and will soon win the game because white has an extra queen.