I like the guide, and there are some good tips in here, but I see it as average (no offense). Mostly, it's the inaccuracy of MU's. Beyond that, I'd like to add a few tips that you could add that would make this an excellent guide:)
1. Ness, Yoshi, Rosalina, and Pikachu are much harder matchups than they seem. Yoshi can be mid, but Pikachu is small enough to dodge more than half of our attacks; Ness has some crazy maneuvers that absolutely demolish ZZS; and Rosalina is a horrific MU to play outside of For Glory. Check out the official MU discussion for ZZS, the details in there are detailed and accurate!
2. For combos, I really can only think of is when your opponent's at roughly 50-65%, ZSS can hit with the back of the Uair, and jump into a Bair. Works any time you have the second jump as well as hitting the back of the Uair.
3. ZZS can pivot, SH, Bair to pressure foes fairly easily. It's a strong aerial, so any person who tries to match you in the air will get punished.
Overall, it was a good guide. If you take my tips into consideration, I'd be more than happy to reconsider my review:)