I encountered this interesting deal yesterday.
Let's say East leads a heart. West must duck the first round of hearts and the first round of clubs, otherwise declarer has the timing to set up two tricks in each of those suits. Then if declarer plays a second round of either suit, West can establish their 4th card in that suit as the setting trick. This is a defensive principle that comes up from time to time, and is worth remembering -- don't be in a hurry to take your aces!
However in this case declarer has an answer: running the spades. West will be forced to discard either both diamonds or the long-card threat in hearts or spades.
You can use the Play button to begin stepping through the tricks, and the GIB button to see a double-dummy analysis at any step.