Because this is IMP scoring, you should be concerned primarily with guaranteeing the contract. So after winning the heart lead, you should unblock the ♣K and then play a low diamond
from both hands. This protects you when both minor suits break badly:
You can win any return, cross to the ♦A, cash the ♣A Q (pitching the ♥2 and ♠2 from your hand) and run the remaining diamonds. True, you’ll give up an overtrick if diamonds are 3–2 or clubs are 3–3, but by playing this way, you protect yourself when they’re not.