Only chance for this match-up to push Zoro to mid-diff (or high-diff at best) is if it's Queen & Smoothie vs Zoro.
If it's Smoothie vs Zoro or Queen vs Zoro, they'd lose low-diff (or mid-diff at best) to Zoro for two reasons: their size and their lack of agility.
Queen obviously isn't very fast (as opposed to King), as seen from his previous action against Big Mom. He is very large and his attacks pack a wallop, but that's it. He is like Pica in that sense and if it's Queen vs Zoro, Zoro will just spam his large-scale attacks until Queen's defense falters and then he will finish Queen off mid-diff at best. Queen's long neck in his Brachiosaurus form is a very vulnerable spot. If Zoro aims for that with Enma + Current Asura/Rokudan no Tsuji + Armament Haki, then Queen goes down like he's paid to lose.
Smoothie is a bit tricky to gauge since she doesn't seem as competent as either Katakuri or Cracker. Also, she did not display anything special when chasing SHs in WCI and she couldn't do a thing to anticipate King's attack, so I doubt she had great speed or reaction time. Her downfall if pit against Zoro is sealed basically because, as hinted in WCI, she grew bigger and bigger during fights for reasons unknown, so, just like Queen, she will only end up giving Zoro a larger target. It would be another Zoro vs Straw Monster. Enma + Current Asura/High-tier attack(s) + Armament Haki can certainly bring Smoothie down.
But, if it's Queen & Smoothie vs Zoro, then yes they can push Zoro to a mid-diff due to outnumbering him and more range & power in their attacks. They should get several good hits on Zoro, but not too strong to put him down for good, before they lose eventually.
This is why I think King vs Zoro is the only match-up where Zoro can be properly tested since King's speed + attack + reaction time are tops. King vs Zoro is a high-diff fight at worst and an extreme-diff at best.
However, with Zoro being predicted to help out against Kaido (to at least slash him once with Enma and give him a fatal wound), then I am now starting to see that Zoro vs Queen or Zoro vs Queen & Smoothie is indeed a possibility, because, as I said above, this match-up is mid-diff at best for Zoro, so he will not sustain any injuries that would impede his participation in Kaido's defeat. Whereas a match-up against King is certainly going to be a blood bath and would, therefore, cast doubt into his participation against Kaido.
But, honestly, if Zoro mid-diffs Queen or Smoothie or Queen & Smoothie, the only thing I know for sure is that the "Oda wanks Zoro hurrr durrr!" accusation is back in business.
From a personal POV, I certainly don't mind seeing Zoro mid-diffing a guy with a bounty 1 billion berry higher than his own. It would put to rest any doubt about where he stands right now, tbh.