Here's a harder one. Find the kernel of the discovery: White’s knight masks his queen on the seventh rank. If the knight moves, the queen again has no piece it can target—just a pawn, and a protected one at that. But once more you examine the Black king and find that the queen would have a great square to attack: Qg7 nearly would be mate; only the Black knight on e6 would prevent it. Now the important thing when your pieces close in on the king like this is not to think about the two halves of the discovery in isolation. Think instead about how the two parties to it—here the knight and queen—can help each other. If White plays the discovery 1. Ng5, he threatens NxQ. More significantly, though, the knight also attacks another square next to Black’s king, thus creating the new mating threat Qh7#. Against this idea Black’s knight is no help. He is forced to play 1. ...Rxf6, as this erases the immediate mate threat on g7 (by removing the protection White's queen would have there) and also gives the king a flight square (f8) if White plays Qxh7.
At this point it might seem natural for White to complete the sequence by playing 2. NxQ, but that would be a mistake. Black then would have RxR+ (easy to overlook!), leaving White still with a winning advantage but not an immediate win. Your first order of business when you have pieces bearing down on the king is to look for mate. While Black’s move Rxf6 ends the threat of 2. Qxh7#, the move 2. Qxh7+ still takes control of the Black king’s fate and keeps the initiative, comfortably postponing the capture NxQ through the priority of check. Black’s king is forced over to f8. White again has a chance to play NxQ, but once more he waits, preferring instead to bring another piece into the mix with RxR+. Black’s king is forced to e8. Now White plays NxQ, having used checks to keep that capture available for two moves. Black’s knight, his last remaining piece, has no safe place to go, and will be lost next move—leaving White with a queen, rook, and knight and Black with no pieces at all. Mate follows shortly.