I think it's interesting to look at the word used for "hell"
Zoro uses Jigoku when referring to being the King of Hell
Hiyori uses Jigoku to describe Wano
Kid and Beast Pirates used Jigoku when describing Kaido and Big Mom
I think word use is interesting because Zoro doesn't use en, naraku, or any other word which describes hell. It's even more interesting when you realize Zoro uses En-O for his technique, but use Jigoku no O for his epithet. Which mean there is a deliberate reason behind his choice of words.