First of all, ZSS:Wario and ZSS:Marth are 50:50. I think ZSS:Marth is in ZSS's favor, but nobody else on my board does.
ZSS's flaw is that she basically has no grab. People can shield and can dodge the grab on reaction, which is stupid. That being said, her shield problem only affects her vs. a few characters. MK, Snake, Diddy, and a tiny bit Marth. Everybody else she can hits shields with spacing moves, and not get punished for it. (lol d-smash, so "terrible')
All that being said, if ZSS DOES land a grab, her throws are good. F-throw is a CG against heavies, d-throw puts people in combo positions (Uair is sometimes guaranteed.), b-throw can lead to a follow-up, and u-throw... is good on teams... yeah... She also has GR CGs on Squirtle, Wario, MK and Pikachu.
Her ground game is mediocre. D-tilt is good, and puts you in the air. It has enough cooldown to get punished on PS though. F-tilt is TERRIBLE! Her worst move IMO. U-tilt's hitbox is stupid huge, and it puts people in the air again, so it's good.
U-smash is okay, the big hitbox being it's only purpose. F-smash is bad, but it has uses. (It's a kill move, sometimes!) D-smash is one of her best moves, IMO. It's a stupid-good damage-racker, stuns people for a guaranteed follow-up, can punish landings, AND the hitbox is HUGE! (See my avatar)
Her air game is where she really shines. Her dair is usually bad. It autocancels... really high up... so it's ntop good for that purpose. It's only real purpose is the slight stall it has at the beginning, to dodge an attack (yes, I am not joking) and then hit with it. Her fair is decent, lots of damage if the two hits connect, but they probably won't. Bair is amazing! It's spacing is too good, it has low landing lag, and you can do two of them in one SH.
Uair is much better than any of her other aerials though. It's hit box is amazing, it leads into itself, if you air-dodge one of them, a second one will probably hit you. It's hitboxes even beat every one of MK's aerials... AND it's like 4 frames.
Her specials are good. Paralyzer is slow and only has two states, uncharged and fully charged. Even with those limitations, the move is okay. Running b-reversed paralyzer is probably it's best use. I'm running away, and now you're stunned.
Plasma Wire (Up-B) is probably her best special. It's the highest hitting move in the game, and it has 4 or 5 hitboxes that all do different things. it can do a slow spike, and fast spike, or it can leave you where you are, which is good for follow-ups.
Her Plasma Whip (Side-B) is the second farthest horizontal hitbox in the game. It's slow on start-up, but it's good for catching dodge, and landings.
ZSS is so weird to use. To use her the best, IMO, is to punish whatever the opponent does to you. An aerial hit your shield? Punish. Somebody is landing? Punish. That's how I play at least, and it works pretty well for me.
Also, don't think you can pick her up and be amazing with her. She's... retardedly hard to use. Top 5 hardest IMO... Not technical-wise, but having no grab makes you re-think how to do things.
I think I'm done.