Is it possible?
Apple site says it can run two 4k displays. But can it drive them both at 60Hz?
Upd. Question was marked as duplicate, but this is not fully correct - 2015 MBP 13 and 15 have different integrated video cards from Intel. And surprisingly 13's card is better than 15's ( 13 - Intel Iris Pro 6100, 15 - Intel Iris Pro 5200).