Adapt is right, make sure you can recover properly without getting gimped, it's the first step on the ZSS ladder. If you need help, check out Snakeee's thread
here. Once you feel confident in being able to return without getting gimped, you can move on to other things.
There isn't really a good guide on how to space properly with ZSS, but that should probably be your next focus. Learn the ins and outs of her Side-B, aerials, tilts, and grab. Your general gameplan as a ZSS is space with side-b and then punish any approaches with aerials, d-smash, and tilts.
Quick scenario: throw out a side-b so that the sweetspot lands just in front of opponent's shield. They slide back, drop shield, and begin dashing forward. You retreating short hop, preparing to do another side-b, but realize they'll be too close (on the close side of the sweetspot), so instead you n-air, they shield, you d-tilt to pressure, they get hit out of their grab, and you follow up with u-air. etc etc.
The point is, pressure the approach with side-b, and then pick it apart with your fast aerials and tilts, and maybe a d-smash with good spacing. (A
good great thread to get info about all of ZSS's attacks is Adapt's thread, right
here)
After you learn spacing, you should learn how to deal with shield pressure. Since ZSS has a bad shieldgrab, you have to rely on other out-of-shield options. Try different things, u-tilt, jab, d-tilt, u-air, etc. Find what you're comfortable with, and what works in which situations.
After that, learn combos. They're gonna be your best form of racking up damage. I don't mean to plug myself, but I've got a thread on combos right
here. Once your opponent is in the air, they shouldn't touch the ground without taking 10-20% damage, if not more.
Finally, learn edgeguarding. It's like the mastery of your recovery, and it's a great way to get some kills. Knowing exactly how to edgeguard each character is important, and it's something we're currently working on in the match-up thread (found
here). Until that list is completed, you should practice connecting with b-airs off stage for edgeguards and d-smashing people coming off of the ledge.
Other than that, it's the mastery of each matchup, which the previously mentioned matchup thread should help with, and learning the little quirks about ZSS, (like a lot of stuff found in Adapt's odds and ends thread,
here)
and of course, posting on our Q&A thread is a great way to get some help! Happy hunting! d;