In the background. Are Billy Gibbons and Dusty Hill the Z's and Frank Beard (the drummer without a beard) the Top?
The title of the video is John Fogerty and ZZ Top. Z2 and Top must be off camera. Somebody is playing bass and drums.
You are expecting Mr. Creedence C. Revival to be playing with Mr. Z. Z. Top? I wonder where Mr. Jethro Tull is?