the person inside spiral zetsu is most likely yamato

[osba]

the 2 zetsu's were talking "telepathically" (at the same time)
this means that whoever is inside, is not in charge.
we know how yamato got delivered to obito, and obito worked together with zetsu (kabuto even said he could make them stronger with yamato)

 

[CDT23]

It could be, that way if he makes more clones they would be Zetsu clones. In theory that is
I would like to see Yamoto back in action. Please not another Uchiha, the only one i can think of that it might be, is Izuna. Maybe Madara used his eyes to bring back Izuna, and thats why he needed life support from the tree. Like how Obito is being kept alive by Zetsu. Or it could possibly be Shisui and he got brained washed to be evil too. That would be a hell of a mind blown. And it would mean that there was 2 Tobi running around.

 

[osba]

It could be, that way if he makes more clones they would be Zetsu clones. In theory that is
I would like to see Yamoto back in action. Please not another Uchiha, the only one i can think of that it might be, is Izuna. Maybe Madara used his eyes to bring back Izuna, and thats why he needed life support from the tree. Like how Obito is being kept alive by Zetsu. Or it could possibly be Shisui and he got brained washed to be evil too. That would be a hell of a mind blown. And it would mean that there was 2 Tobi running around.

izuna would not need to be restrained against his own will by spiral zetsu and shishui would be no good without his eyes.