I find Zach a difficult character to like, lacking the charm of goofball friends from other games like Derek, Liam, Chris, Jacob, etc. You always had that friend who was cool in small doses but wouldn't shut up. I think he is supposed to be that way, though.
It makes me wonder... if there's a choice in the future that he takes as a betrayal (e.g. messing around with Valeria, ignoring him in pursuit of Layla/Erynn, blaming him for something that happens at camp), could that be another Julia decision? He blabbers about your escapades and unfaithfulness and it ends the Layla and Elena paths. By contrast, if you stick by him, he vouches for your character to Layla should the juggling with Lexi get revealed to her at an inopportune time.