Zoan is one of the three Devil Fruit types. This type of Devil Fruit allows a user to transform into an animal species at will, or an inter-species hybrid.

Like all Devil Fruit abilities, Zoan types can be “awakened”. Zoan type awakenings don’t affect their surroundings, instead the user develops a striking new transformation, with their bodies typically becoming tougher and their personality becoming duller. However, awakening a Zoan fruit comes with a risk of the innate nature of the fruit’s respective animal consuming the user, causing them to lose their personalities and become simple-minded beasts.

In some rare cases, though, Zoan users can retain their personality upon awakening their fruit. In these cases, rather than degenerating into a mindless beast the user will gain access to a powerful new Awakened Form in addition to their previous transformations. This form is characterized by flaming hair and a scarf of flaming smoke appearing around the user. So far, only Monkey D. Luffy, Rob Lucci, Kaku and Jaygarcia Saturn have demonstrated this ability. Yamato also gains flaming hair and what appears to be a ribbon-like trail of cold air in both their hybrid and full Okuchi no Makami forms, but it has not been confirmed if this is the normal transformed appearance or an awakened form.

Mythical Zoan Devil Fruits are the hardest to awaken because of the need to embody the entity itself which is varied by nature. Regular Zoans don’t have this issue given normal animals are simple by nature and don’t require that much to awaken them given Kaku and Lucci were able to do it within 2 years.

Luffy embodies Nika and the things he stood for and because of that he was able to awaken in the face of certain death.

Kaido’s devil fruit is an Azure Dragon and those are sacred treasure guardians and protectors of freedom. Kaido embodied none of that. Momonosuke has a better chance of awakening down the line in all honesty. Kaido represented the exact opposite of his devil fruit and that’s why I think he’ll never be able to awaken it.

Sengoku having the Buddha devil fruit while working for the World Government means he most likely isn’t awakened either. No way can you become “Enlightened” while working for people who seek to smother knowledge. Sengoku could probably awaken now that he’s become more relaxed and taken a bigger look about what he and the World Government has been doing all these years.

Yamato has a very high likelihood of being awakened given she HEAVILY embodies her entity but I’ll wait for Oda to give her the confirmation. She has no reason not to be awakened and could explain why she was able to go toe to toe with Kaido for as long as she did.