Zaire is a big kid, but let's see if he can hold up over the course of a season. At minimum, Golson is the best backup in the nation (depending on the OSU situation).
That being said, Golson is a better passer. With protection he's one of the best in the country. Perhaps the biggest distinction between he and Zaire is his instinct to pass when the plays break down. When he scrambles, he's always looking down field for the pass. Obviously that is a double edge sword. Zaire looks to run when the play breaks down.
I suspect that they can bring the best out of each other if Kelly manages the system correctly. He did it with Pike and Collaros. The question is whether Golson wants that situation (and whether he can do anything about it if he doesn't).