It's very difficult to tell. I doubt it's a mythical Zoan tho:
For once his environmental manipulation effect is far too great and widespread and for the Nika fruit it's also just a thing because Luffy's body is rubbery, so he makes other things he touches rubbery aswell (on a very small scale) but he's not actively turning things into a latex like substance. Whereas Greenbull on the other hand is summoning whole forests wherever he goes.
Secondly it looks like his main ability is him turning into roots or plants, instead of transforming into an animal like- or humanoid being, that then has a certain special quirk.
Yamato is not turning into ice, she's just creating it. Even Marco is not really turning into phoenix flames, instead he's just making use of these flames that are given to him by his phoenix transformation.
Greenbull would have to be some kind of druid esque being that somehow can turn its body into roots or plants, which does not add, as that specific transformation quirk would rather be linked to a special paramecia or a logia, which also explains his incredible environmental manipulation technique.
I can't decide between those two tho, as both could be possible imo. You also couldn't tell the difference between Kuri and logias and in this case plants are even a natural phenomen.
For once his environmental manipulation effect is far too great and widespread and for the Nika fruit it's also just a thing because Luffy's body is rubbery, so he makes other things he touches rubbery aswell (on a very small scale) but he's not actively turning things into a latex like substance. Whereas Greenbull on the other hand is summoning whole forests wherever he goes.
Secondly it looks like his main ability is him turning into roots or plants, instead of transforming into an animal like- or humanoid being, that then has a certain special quirk.
Yamato is not turning into ice, she's just creating it. Even Marco is not really turning into phoenix flames, instead he's just making use of these flames that are given to him by his phoenix transformation.
Greenbull would have to be some kind of druid esque being that somehow can turn its body into roots or plants, which does not add, as that specific transformation quirk would rather be linked to a special paramecia or a logia, which also explains his incredible environmental manipulation technique.
I can't decide between those two tho, as both could be possible imo. You also couldn't tell the difference between Kuri and logias and in this case plants are even a natural phenomen.
1. Mythical zoan have their own unique abilities that can even be an amalgam if all three df classes
2. It's zoan centric arc
3 we got the sun god (nika) and there's still the gods of the forest (greenbull?) Rain and earth left