In a performance at her Vegas residency, JLo performed a tribute to other singers by covering their songs in a medley.  One of those people covered was Zedd, and Zedd didn't see it coming, but he loved it!

The medley begins at 5:25 with Lee Ann Womack's "I Hope You Dance" -- the snippet of Zedd's "Clarity" happens at the 9:03 mark.

Latin Times says was in the crowd, immediately tweeted.