By now the queen-and-rook kernel for Black on the long diagonal no doubt is obvious. Look for a target for the queen if unmasked, and see that White’s queen is loose and ready to be taken on c3. Black just needs a threat to make with his rook on e5. The rook can’t directly threaten anything at the moment, but the key fact about the piece is that it is part of a battery of rooks aimed at White’s back rank. Play through the first rook capture in your mind’s eye: 1. ...RxR+, to which White replies 2. RxR. Now what? The answer is tricky. Are you inclined to play 2. ...RxR+, checking the king? Not so fast: White’s queen protects e1, so White would be able to play 3. QxR, taking the queen out of danger and dissolving the check at the same time. Any other ideas?
Consider the surprising 2. ...Re2, which puts pressure on a square next to White’s king (f2) that Black already attacks with his queen. This allows Black to threaten mate with 3. ...Qxf2; White must do something to prevent it. If he plays 3. QxQ, Black doesn't recapture right away with g7xQ; rather, he first plays RxR+, winning a rook and checking White’s king (the priority of check again). After the king moves to h2, then Black still has g7xQ—and only Black’s rook is left on the board. If White instead plays something other than QxQ on the second move of the sequence, Black plays QxQ on his next move.
The hard part of this position is seeing the value of Re2 for Black. The key point to remember is the sensitivity of squares next to the king, especially when they already are attacked by a queen. Adding another attacker against such squares, as Black does here with his second rook, can create a crushing threat even if no check or capture is made with the move.