West plays 6♦ on a club lead. The ace is taken, then the ♦T is covered by the king and ace. A club to the king is transportation to run the ♦9, covered by the jack and queen (south discarding a club), then a trump is played to the 7, south discarding a heart, leading to this position.
A club is led to the queen and south has no good discard. If he discards a spade, the king and ace of spades are followed by a spade ruff and the 7 is established. If south instead discards a heart, the ♥AK are taken instead, a spade is played to the king, and a heart is ruffed. North can over-ruff but E/W take the last three tricks with the ♠A, a trump, and a heart. This squeeze is on even if north doesn't cover the diamond leads from the west hand.