So Zoro clears Lucci once he actually uses a named attack.
The fight was long, but duration of off panel fights don't matter that much (see e.g. Zoro vs Beetle Gifter).
Once Oda decided to focus on the fight, and the characters involved used named attacks Zoro quickly dispatched Lucci. I don't really care to debate whether this is a low diff or mid diff, but it's at least a comparable (if not better) kind of domination over Lucci as Nika did. And Zoro did this without using his Wano power up/strongest form.
Base Santoryu Zoro is able to dominate Lucci level characters.
I think many folks here need to revise their assessment of Zoro's power level upwards.
Cc:
@Fujishiro,
@TheAncientCenturion,
@EmperorKinyagi,
@pg13