First of all M3 was a thing created by fans and now m3 is zoro sanji and jimbei ? wtf lol!
OT : simple sanji and jimbei seems to be close in strenght. So if they fight a t6 it follows the things that Oda showed till now.
Jimbei was equal to ace and we know that ace was not in the top 3 fighter of WB (marco, jozu and Vista) so if jimbei doesn't fight a calamity it's not a big deal. Actually if sanji fights queen and zoro fights king, it's not possible for a jack vs jimbei because neko and inu need to take their revenge in their suulong form. Unless Oda forgot about that.
For Sanji even if he dominated P1, it seems he doesn't defeat him so him fighting a stronger one like drake or Who Who is pretty much a good thing, considering his previous fights against vergo or doffy. But for the story and luffy's dream, EOS sanji needs to be at least yc2 lvl so we have time for him.
For Zoro, i'm not worry. Oda is the biggest zoro wanker so impossible for him to let Zoro fighting a weaker opponent than king.
But if it happens, I will be so fucking disappointed if he doesn't fight king or the second strongest in Kaido's side. But king is too dope to not be a zoro's opponent. Oda always gave to zoro an opponent who has something special. Monet being a logia and defeated her without haki, one shotted Hodi in water, cut a mountain size golem, won the first SN battle in an unique way.
Oda also gave him "enma" with a special ability when zoro didn't show his full power, that's why it will be disappointing and dumb to skip zoro vs a calamity or the second strongest.
So the only question is "kaido has someone stronger than king or not ?" If yes, zoro will fight him and if no, zoro will fight king.
No one in the alliance except Luffy and Zoro can take King or the "Ace" if there is one. But luffy will fight kaido supported by law and kidd.
Zoro vs King a pure 1 vs 1 swordsmen battle.