KoH is just the name Zoro call techniques that uses hell flame, overwhelming CoA haki or whatever it is combined CoC.
KOH = Hell Flame + All Out Haki .
This would explain a lot of things :
> For Hell Flame :
It seems consistent because Zoro claimed to be the King of Hell so he has to have the Hell flame especially with Usopp's lies turning out to be true each time , and what's funny is this flame is really strong even against magma like flames they showed a clear superiority .
> All Out Haki :
1--> Overflowing adv CoA :
we thought that Green Aura is the smoke of Zoro using a great deal of HAKI , but there is always an issue :
1/ Enma takes the same amount of Haki that Prime Oden used to give it , and that is confirmed by Zoro .
2/ Those Auras were never seen with Oden a single time .
So those auras we said it's related to overflowing haki isn't true , and aside this when we have Zoro using it again are we gonna say Zoro didn't master it since apparently this visual will stay with Zoro to show he's using KOH ?
In Other Words , there is no effect for knowing Overflowing state of Haki besides usage of KOH , while in regular cases it's just Zoro using his regular amount of CoA .
2--> Adv CoC and it's Overflowing State :
Adv CoC is the answer for durability monsters , and Zoro uses it in two styles to the point his dragon style mid level technique has a similar portrayal to Togen Totsuka which is Prime Oden's ultimate that put Kaido near death and that says a lot about KOH Mode Overall.
Food for thought , Oden got enma for years and he never got to have KOH title and achieving Hell flame ; Base Zoro right now is like having Prime Oden's strength coupled with Hell flame and that put him in the high level spectrum of Mid Top Tier if not High Top Tier and the only thing that differs him and Shanks ( 2sd strongest swordman ) is lacking Future Sight .