Nah, King of Hell is Zoro using Overflowing Ryuo plus Haoshoku coating.
Zoro can use overflowing Ryuo alone:
Overflowing Ryuo is basically what Zoro did for his Rooftop attacks.
See e.g. Hiryuu Kaen:
Or Kokujo Ou Tatsumaki:
And he can also use Haoshoku coating alone:
Combining the two is when he uses King of Hell:
Zoro can also do overflowing Haoshoku coating for "King of Hell Three Dragon Style":
There's no black lightning in the panels according to the spoiler provider, so this isn't Haoshoku coating, just overflowing Ryuo.