Oda is setting the stage for him to be able to fully utilize the power he's been releasing constantly.
Like I currently rank him low top tier or borderline low top tier. And this is him without being able to use acoc while knowing he has it.
When the flashback is over there should be a little training arc for zoro so that he masters acoc.
If he masters it, where do you guys rank him? I personally would rank him solid top tier after he masters it. He will be ready to face Mihawk after he masters it.
Two hints.
1. His body has already strengthened to be able to release a lot of Conquerors haki without sweating.
2. Enma draining too much haki in Wano will no longer be a problem.
So in practice, he is able to wield Enma like a feather just like Oden since his body has caught up to the haki drainage.
It's likely that this is the arc that represents Zoro's ascension to becoming The King of Hell. He will at least be on par with Oden by the end of the arc.