I think the zombie face think is mainly an internet created myth. I mean, you can use Google and find such pictures, but the explanation is other than just taking a GLP. In the most prominent example, the one which returns highest on the search results, the "celebrity" pictured is now Middle Aged, where as before he was younger, and he has practically killed himself, ruining his health, with alcohol and recreational drugs. That combination of factors makes for the difference in the appearance of his face along with the weight loss.
I do not think the bodybuilders here using it are going to look like that, even though I do not support its use (completely unnecessary to cut, for bodybuilders or fatties).