Current Santoryu Zoro is a low top tier, but the only significant improvements he's made is learning to cut fire and haki (via Enma training).
However, New World entry Zoro would also have had:
* (Upgraded?) Asura
* Whatever is up with is eye
1. Zoro is nerfing himself
2. It's a limiter (Kenpachi's eye patch)
3. He lost it in a duel with Mihawk (flashback needed)