Declarer has 2 diamond losers and a club loser. That is if trump behave. Clearly with weak trumps in his hand he can't ruff the minor suit losers on the board. It looks like we will need to setup dummy's long suit.

Win the K lead and ruff a heart to hand. As the opponent's follow, hearts prove to be 4/2 or 3/3. Therefore we need at most two more dummy entries to lead hearts (ruffing in hand, or discarding once) and one dummy entry more to enjoy the long hearts. We have four entries, two in trump and two on the side. So you can draw trump ending on the board (there is an alternative of playing only one round of trump to the dummy). Ruff a heart (they go 4/2) with your last trump and use one of dummy's remaining entries to go back to the board to lead and lose a heart. The dummy's hearts are now good and you have one entry left to enjoy them. You lose only a heart to take 12 tricks. If trump had gone 4/1, you would need 3/3 hearts.

The field did pretty well on this hand. Bidding and making 6 was worth 5.1 in one section and 6.5 in the other. Two pairs made 7, they likely played to Kafter the initial heart ruff and ruffed another heart in hand. Back to the board with a side suit entry to ruff a third heart in hand, over ruffing West if necessary. Now use the last side suit entry get to the dummy, draw the last trump and claim. The analysis of how many rounds of trump too draw and when on this hand is a bit complicated for the space available.