I just try to stick to the point, and discuss with an open mind, and respect for others. Some people don't do the same, but it's best to just ignore it and stay focused.
Whatever. I have bad matchup experience with ZSS. http://www.youtube.com/watch?v=HEh5_1gWUtA
I'm afraid of watching that nightmare of a video.
Anyways, here's the lowdown. ZSS is fast. There are a couple of things you should learn, for example, her Up B can spike, and it doesn't leave you helpless like Olimar's UpB. If you're recovering from above, watch out for this. Her side B is really good. It has great knockback, and is one of her best kill moves. I don't know much about her down B. Her neutral B has short range, but it can stun. Fear her Dsmash, since it stuns you for like 2 seconds. This is a combo starter, and a free kill, if she does it when you're at the ledge. Her Fsmash is bad, and they never use it. I don't remember what her USmash is. Her Uair is their best move apparently. It has massive priority, and decent knockback. Dair is never used. Blah....
ZSS likes to combo a lot, and with her speed, it's not difficult for her to combo. Just don't freak out like I did, and pay attention to what's happening.