Zoro's swords appear to not be hardened in the page where he's clashing with Awakened Lucci:
After trash talking Lucci, we see Zoro harden his blades with accompanying haki tendrils:
However, these tendrils resemble overflowing COA/Ryuo more than the black lightning of Haoshoku coating.
For example, when Zoro first received Enma:
When Zoro was blocking the Bird Cage:
Even random fodder like Raisin could create (albeit smaller) haki tendrils when hardening their sword:
The black lightning of Haoshoku coating tends to be much bigger in relation to Zoro's swords:
I think what's happening is Zoro starts to unleash his COA more on the last panel we see of their fight.
I don't think Zoro has unleashed his Haoshoku coating yet, but that might change when we get the "Zoro vs Lucci" chapter.
Cc:
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@comrade,
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