If you would like to solve the puzzle yourself before reading this post then please follow this link.
The starting position of this puzzle is like this with white to move:
I wanted to show this puzzle because it has two nice mates and you only get to see one in the trainer. The first move in both mates is 45.Re8+ followed by 45..Kh7. In both cases the second check is 46.Qf5+ after which the position looks like this with black to move:
On Lichess, black's next move is 46..g6 after which 47.Qh3+ forces 47..Kg7 and white can mate with 48.Qh8# :
The second mate happens when black replies with 46..Kh6 after which the position looks like this with white to move:
This allows a second mate in which the white queen, black pawn on g7 and rook mate after the move 47.Rh8# :
I hope you enjoyed this puzzle and you can have a look at the game in which this tactic appeared here.