Speed control is a problem because this is literally the most free low kick for scarf Koraidon ever. You cannot make that sht up. This is literally scarf Koraidon's wet dream, click one goddamn move and barely get punished because Eternatus is not switching in to Koraidon at all
I'll go with the small changes first
Ting Lu
Use specially defensive EV spread on this. You're not stopping the fking nuke if you're not specially defensive. You just die almost instantly. Also, use tera water on this so if things get worse, you can use tera to emergency check Kyogre
Arceus
Use silk scarf over life orb. The tier is already hazard infested as it is. You do not want to lose your life. You should also use taunt over flare blitz. Flare blitz does jacksht for extreme killer and Skeledirge is common and you do not want to get burned. As mentioned earlier, this team is scarf Koraidon's wet dream so don't let it get away with it. Use tera ghost on Arceus so you can dodge the incoming low kick and you get stab on shadow claw. Do not replace shadow claw with anything because you need this to hit Giratina otherwise it just walls you and taunt ensures you do not get burned. Don't play mind games with the thing, taunt it. You might even force a tera steel
Zacian
The thing about this team is you can easily lose to webs Ribombee. Zacian with substitute and tera flying ensures you never lose. Sub blocks stun spore and obviously you destroy it. Now, Ribombee has adapted by using quiver dance so they break your sub with moonblast despite the resist so you'll have to play some mind games but it's one you're favored to win. Also, use tera flying on this. Just based on my experience, tera flying sub Zacian can instantly win games on the spot. Just tera and sub on Groudon or Landorus and it's game over because chances are, if they have either of those ground types, they don't have a Skeledirge or Toxapex. You can choose between close combat or play rough on which one to drop, I personally prefer dropping play rough so I don't get walled by Giratina
Eternatus
Use specially defensive spread on this one. Don't go fancy with cosmic power stuff because Uber is an insanely volatile tier and a good player will stop you from racking up these boosts not to mention recover now only has eight pp so you're really handicapped. However, it still fills an important role in absorbing toxic spikes and a Kyogre switchin. Funny thing about it is it also doesn't get two shotted by most Flutter Mane so this might come in clutch
Now, for the big change
Kyogre/Miraidon --> Koraidon
Speed control is an issue with the team and there's no better speed control option than the best pokemon in the tier, Koraidon. Yes, Koraidon is better than Miraidon now. Deal with it. Now, the replaceable slot on this is either Kyogre or Miraidon, I chose to keep Miraidon because it's generally a better pokemon. However, the bottomline is one of Kyogre or Miraidon has to go. Either one can really work on the team, it doesn't matter which one as long as its one of them and scarf Koraidon. However, be careful of Flutter Mane. For one reason or another, that thing is always faster on sun even when using life orb. It speed ties Koraidon but it wins every time, dunno why
Here is a sample team with all the changes. You can also pull off some really fun stuff by altering the team a bit and having this
The first team is a more offensive team. You'll have to play aggressively on that team and destroy stuff otherwise you will lose to scarf Koraidon and the defensive backbone isn't that strong especially since you're fairy type is Zacian. If you really want, it is a very good idea to go tera fairy on Koraidon over the standard tera fire just so you can take whatever the opposing Koraidon throws at you. The second team is slightly more defensively stable due to Arceus Fairy and is significantly more threatening once Koraidon gets those scale shots going but isn't that reliable because scarf Kyogre is outsped by the best pokemon in the tier
Now, take note that both teams are REALLY vulnerable to Arceus Ground, dragon dance or calm mind. Here's the thing about Ubers, if you want to be defensively safe against all pokemon, you're gonna have the exact same team all the time, not that you won't have it in the first place. That's just the nature of Ubers, you have to keep up momentum or you almost lose on the spot. Hell, you can even lose to a tera steel agility calm mind Miraidon if you're not careful. The point is you have to play offense. The only way to be safe against Arceus Ground is Giratina, who also carries defog, and while it is also a strong pokemon on its own, you'd have to give something up. If Arceus Ground is too much of a problem, replace Zacian on the Miraidon team or Eternatus on the Kyogre team with Giratina
