In Chapter 1110 the Five Elders are now fully gathered at Egghead and undergo their Zoan transformations.

My theory is that the Five Elders are NOT Zoan Devil Fruit users. There was no Devil Fruit named when the Five Elders were introduced. Why? Because they are the “Devils” that turn into the fruit once killed. Those creatures are their true forms and have taken over “vessels” of past citizens who have died and taken their appearances.

Joy Boy is not a Devil Fruit user either. After he was defeated by the 5 Elders, people wished his return which created the Gomu Gomu No Mi (Nika’s devil fruit). He is the fruit which is why Zunesha thought Luffy was Joy Boy (he is lol).

The 5 Elders never died so they never turned into a fruit. Gomu Gomu No Mi hasn’t had a user until it manifested Luffy to eat it. Imu and the Five Elders are from the Void Century and will annihilate anyone who threatens their existence. Imu took over Nefertari D. Lili’s body as a vessel and we aren’t going to see this until later on.