Familiar principle, different context. Black’s queen and White’s queen attack each other, with each enjoying protection from one of its fellow pieces. Don’t just think about whether to exchange queens; think about whether you can knock the legs out from under White’s queen by paralyzing its guard. Or just think about any checks Black can give. He has two to consider: Qh2+, losing the queen without benefit; and Bxf2+, which forks White’s king and rook and invites the reply KxB. What would be the significance of that exchange? When a move would force the enemy king to change squares, look for fresh pins. Here White’s king would step behind the knight on f3, causing it to become abruptly paralyzed by a pin from Black’s queen.

Having seen that you have a check which results in a pin, ask not just whether the pinned piece can then be taken but whether it was serving defensive purposes that might now be unattended. The knight was guarding White’s queen, so now Black takes it with QxQ. Shouldn’t Black worry that moving his queen to play that capture also will release White’s knight from its pin? Yes, he should worry about it; but Black’s rook on f7 picks up the pin once the queen leaves the file.