ZSS wants to keep you in midrange until she can hit confirm you into a combo or string. She has the zoning tools to do this, but her primary zoning tools still have enough commitment that we can sneak in and punish, since our mobility is on par with hers. She can't generate a lot of shield pressure, and with a tether grab, a big part of her game is conditioning around shield, and either scaring or baiting you you out of shield, or hard reading that you'll stay in shield. Learning the conditioning habits of the player is critical, so you can work around them. For example, here is a video tutorial from the ZSS side that details some of the mindset of a ZSS that is trying to condition you (he refers to it as sequencing, and yomi).
From personal experience, some of the conditioning habits I've experienced is a ZSS that would mix paralyzer > dash grab with paralyzer > hipcheck/run-past pivot ftilt, to catch my defensive options. I've also experienced a ZSS using sh zair once or twice in succession to condition me to stay on the ground and shield, and then going for a dash grab. There are other potential patterns, not to mention safe spacing and pressure with moves like nair, which can also string into a combo at low-mid percents.