Zairs still tear Bowser to pieces. Even more so now that he's even taller.
A few things to note about Zairs.
First, it's not possible to fast-fall a Zair unless you do so before the Zair comes out, even better, it's not practical at all to Zair after fast falling from a short hop because it either won't come out, (Link/Toon Link) or the range will be pitiful (Samus/ZSS). Samus and ZSS can full hop to do a fast fall Zair with full range, Toon Link cannot because it'll barely come out and Link just falls way to fast. Samus and ZSS cannot hit a standing Bowser with short hop Zair even from close range because they jump too high, so they can only use it as an air-to-air walling move when you try to jump, otherwise you have till they land, which cannot be mixed up because they won't be able to fast fall, to punish them if you are on the ground. Link and Toon Link can hit standing Bowser with short hop Zair but they won't hit you when you're shielding because of how Bowser curls up in his shield. Also, Zairs are only actives at the tips, and are not active the entire time they are out, they lose active frames and become harmless after they are fully extended.
Now Samus and ZSS could just short hop then do a falling Zair from the peak of their jumps, but that gives it quite a bit more start-up and makes it easier to react, so Link and Toon Link have the most dangerous Zairs since they can just do it during the short hop to hit us, but even if they rising Zair, the zair will last during the entire short hop, so if you see a Link spacing Zairs at you, you could try to wait till it's fully extended then move in or, if you have room for it, you can try to run-in shield it then advance past since only the tip will actually hurt you; air dodge cancel specials would probably work too. Hopefully, this is helpful to anyone having trouble with Zairs in their match-ups.
Also, on Link's jab, Bowser's Jab 1 slightly ourtanges Link's and they are both the same speed. The jabs will only trade if you're both are in hugging distance and throw jab at the same time. I think learning how to make the most of jab clanks will be important in the match-up since we do return to neutral at the same time, and our fastest viable options from clank range will just clank again if we're simply mashing them out. It is possible that we could just clank till out of range but it'd probably suck to be fighting the Link that decides to just grab or Fsmash instead when he knows your jab won't hit him anymore.