The Squeeze-Trim-Endplay: Hand
This hand is from Test Your Play as Declarer, by Lukacs and Rubens.
Lefty opened 3, and you found your way to 6NT.
The opening lead was the Q, Righty playing the 7. You test the second round of trumps and find that Lefty, who presumably started with 7 hearts, also has 4 clubs. If and when you test the hearts, you will find that Righty had one; if and when you test the diamonds, you will find that Lefty had one.
How should you play the hand?