I think so too!
Juggling alone never makes a match-up that bad.
There's a bit more to it, but I didn't want to give any false information and have ZSS and other ROB players yell at me for being bad and wrong
But, I'll give it to you anyway and risk the backlash.
First of all, even if the ZSS player can't do the infinite, Dsmash gives her oppurtunities for a lot of damage and a setup into a juggling scenario, which is even more damage.
Second, ZSS is really mobile, so camping isn't a great option because she can easily avoid the projectiles (which need to be charged so they can't really be spammed) and get in.
At close quarters, ZSS outspeeds ROB on pretty much everything. Dtilt pops us up into the air and, once again, sets up for Juggling. So does Ftilt. Jab just interrupts everything we do, and she can Jab 1 and run away and not be punished.
So yeah, some stuff might be wrong but that's basically why it's such a crappy MU