I am not entirely satisfied with Jett's rankings, so here are my takes on the ZU signups. I only took into account the people who already played ZU, however outsiders like Leru and shiloh, who are decent players overall, can most likely start in ZU and go positive with enough support.
S
S1nn0hC0nfirm3d - Competes with Danny and TheFranklin for the title of best SS ZU players. Ho3n is very creative in the builder and he most likely will support the NFE and ZU slots of your team. Just be sure to not let him run unviable but funny mon like Duosion and he'll just smash everyone except maybe for Danny. Ho3n is self-sufficient, whic can also prove to be a problem as he is not the kind of person to teambuild with other people, so I don't think you need/want another ZU support with him.
Danny - Unlike Ho3n, he only plays ZU and I don't believe he'll support the other ZU slot much. Danny is still one of the best ZU pilots, but his teambuilding is quite average (with an above average creativity that said). Just be sure to not let him be the only ZU builder of the team, and you should get a top ZU core.
Louna - My french buddy is a bit below Danny and Ho3n when it comes to play, but he is still one of the greatest ZU pilots. He can be very motivated if you let him start and play what he likes. Don't let him alone in the builder though, Louna can sometimes get lost in it and burn out, you really want someone to redirect him in that case. He should get positive and help his teammates with the preparation as long as they are not completely afk.
A
OranBerryBlissey10 - One of the best ZU builders, with very creative ideas. He is also a decent pilot and plays NFE. The only downside is that some his off-meta creations can happen to be quite weak to very standard things, so try to pair him with someone who can recenter him in the builder.
avarice, clean, ninja - pairing these three together because they have the same profile. These three know the ZU metagame, are good pilots, and will help with the prep. They are far from self-sufficient in the builder though, but don't need as much support as afk team tour farmers like TJ and jonfilch. Those guys are the best non-ZU mains you'd want to starting in ZU.
jonfilch, TJ - they won't build or be active in the chat. They will play very well if they care and think your team has a chance to win. If you are drafting them, be sure to have someone who doesn't mind building for someone who will have 0 line in teamchat, and to be ready for them to cancer if your team starts losing.
B
a fruitshop owner, Drud - both used to be good SS ZU players, however it all matters on their motivation to build and tryhard their games. They seem to be quite low with afo not having played an SS ZU tour games since he lost to Bossaru in ZULT, while Drud has been relying solely on Jett for SS building during ZUPL. If they both are motivated, they could be A ranks, or even S, but right now they just are not.
Lustfullice - They are not the same player than the one who got ranked last in ZUPL PR. Even if their ZUPL record is quite bad, I feel like they should be given a chance as a starter and have stepped up a lot since their ZULT debut. I don't know them personally, but it seems to me they are building their own teams. The biggest interogation is if they will be active in teamchat, as I have never seen them post in the ZU discord and I was told their ZUPL teamchat was dead.
Corthius - he builds great teams and is a nice teamchat presence, but his plays are still under average imo. I don't think you want to have him start, but he'd be excellent support for your favorite non-ZU main.
C
5Dots, PrinceOfAllTacos - Both will be active in teamchat and will be self sufficient in the builder. However their teams are not great imo, they can take some wins with them, but I don't think they'll go positive or can support well a teammate. Despite grouping them together, I think you'd prefer drafting 5Dots over POAT, because 5Dots has better metagame knowledge of NFE and ZU.
z3ll1 - ShwifyShiftry has been playing quite a lot SS ZU since the end of ZUPL IV, with good results in Majors. If he stays as motivated as that, he can be a good start who'd go positive. That said, he was previously tourbanned for cancering in ZUPL III and isn't the most active in teamchat. Definitely a risky buy, but he can for sure happen to be your 3k starter who'd go postive in ZU2.
wooper - kinda Corthius-light. His teams are a bit less consistent, but still solid enough to support a tour player and he's a great presence to have in a teamchat. I don't think you want to see him start though.
pannuracotta, gorex, Beraldinho - these three will be active in chat and have already played ZU. However, I think they are a stage under the top ZU players and other tournament players.
D
Xayah, Medeia, Hitmonstars, Aaronboyer - They know a bit of SS ZU, but I don't think they are good enough to start nor to be standalone team support. Seeing how deep they are in my list, I doubt they'll be drafted, but you should still consider them.
Greybaum - he will be active in chat and try to innovate in SS ZU. However, he hasn't signed up for SS ZU which means I don't know if he is actually interested in helping in ZU. I think he can be great to bounce back ideas, but not sure if he is great enough as a standalone builder.
pinorska - had a deep run in SSNL and his ZUPL teammates seem to have loves his teamchat presence. That said I don't find him great at ZU and I am skeptical on how helpful he is at the prep.
edit: Only S-rank was ordered btw, all the other ranks are equivalent imo