I'm actually just gonna spew a bunch of my random thoughts on the matchup.
Umm, it's actually a lot easier for her to land her d-smash then you think. This is mainly due to our obnoxiously large frame and the bizarre hitbox of the d-smash. Beware when she's above you on platforms or above you on the ledge, because the hitbox goes through platforms. If you're standing beneath it, it can poke your shield too. Also, unless you powershield the d-smash, dont try to punish it after it hits your shield, she can whip out another one faster than anything we can do to punish. If you do shield, I would suggest you retreat and return to camping. Also, watch your planking, because if you get hit by dsmash, thats a guaranteed down-b spike on us, and if we're high enough percentage (idk the exact range) then it will kill us.
I think ZSS's best shield pressure option is a short-hop towards(and over) us to bait the shield, then she hits us with u-air as soon as we drop it. If you find her doing that, predict with u-tilt, which is usually good for a few juggles.
If you do grab some of her armor at the start of the match, I think the most productive use is retreating glide toss smash throw downwards (or just a straight up smash thrown down if you're already in a decent position) as it bounces up and down for a while, offering us some protection from her approaches. If she tries to catch it, she will have to do so mid-air, so punish her for it! When it's bounce starts to decrease, catch it and repeat. Also, on yoshi's island and other slanted stages, glide toss downwards can be used offensively, as the slants cause the armor to bounce at weird angles, offering you cover if you decide to approach (which may or may not be a bad idea). Also, if you have the armor in hand, shooting off the gyro into the middle of the stage (between yourself and ZSS) is a great idea, bc sometimes ZSS, thinking that they're better with items, might try and get the gyro. Between the spinning of the gyro and your harassment with lasers, you will find openings to foward throw glide toss the armor piece at her. In this case, if the armor is still fresh, I will try and catch the armor after the throw and then return back to camping, if not, follow up the same way you would try to with any glide toss.
If you mix up your edgeguarding, a surprise run offstage>FF fair can lead to an easy gimp if she gets comfortable recovering. Just be careful with how aggressive you get with edgeguarding, if she uses her down-b, she can just hold the jump button and it will automatically footstool you the first chance it gets, which is basically a free return to stage for ZSS, and it also gives her the chance to edgeguard you.
Side-b is ridiculously easy for ZSS to sweetspot on us due to our massive frame. If for some reason she sourspots it, chances are (without sdi, idk if you can sdi it) you will be knocked into the sweetspot anyway. Watch out for side-b if you chase her offstage while shes in the blast zone, she loves to use this when you cant see her during the startup frames. Also, if you're chasing her, she can easily pull out a wavebounce side-b (or even neutral b for that matter) so watch out.
When you are being juggled, your best bet is to utilize bair and up-b to move around so you are not above her. Our low mobility makes this difficult, however, and more often than not, you will find yourself trying to return to the stage with her below you. In this situation, ZSS holds all the cards and you are pretty much forced to guess ( try and predict based on the way she reacts, chances are you will be juggled a lot and will have many chances to see what she does). Basically, I'll go through each of our options and explain when they do and dont work:
Air dodge- Air dodge only works if the ZSS is out of position or mis-times your fall speed. Her uair is fast enough so that she can uair you right after you come out of your air dodge after successfully avoiding the first uair. Also, her forward air can punish the air dodge with little prediction, and with a little more prediction, she can bair us after the airdodge, which is bad if we're at higher percentages.
Nair- Nair works if we start it early enough that we dont get interrupted during startup frames by her uair, the only problem is, if we are high enough above her that we're safe from uair, that means we're most likely in perfect range of her up-b. If the hitbox of nair hits her up b, then we're safe from the up-b, and if we fastfalled the nair we can usually hit her during the end frames of the up-b.
Bair- This doesn't usually work ever. Basically, it pauses us in mid air without anything below us to protect us... its just asking to get u-aired. I do use it to try and position myself better, but thats only if Im high enough above her where i dont have to worry about her uair. I think that if timed right (and on the right side) the hitbox cancels out ZSS's up-B.
Fair- I dont remember how it goes when you use this, I assume it depends on positioning and such.
Dair- lulz ensue.
Just do your best to avoid her until you touch ground. Throw in wavebounces or whatever to get her off your case. Sometimes, (more often than not) your best bet is to fly over to the side of the stage and recover to the ledge. In this case, just watch out for blasters and side-b's (and the occasional ballsy offstage approach).
uhhh thats all i got right now, feel free to comment on any of that, like I said its been a while since I actually played a ZSS
