Senju dna mokuton > zetsu mokuton
So idk what you're trying to say here. Zetsu increased his mokuton? How is that possible when obito has stronger cells in his own body than zetsu does in his?
The only plausible explanation is that zetsu unlocked obito's full potential, unless you can somehow prove that zetsu has stronger mokuton than someone with hashi's dna.
I personally don't know how to describe this to you. I'll try though =D
Senju DNA Mokuton is Zetsu Mokuton. Zetsu is originally made out of Hashi's cells. Zetsu was then cloned several times. Obito did not know how to use the Mokuton abilities so Zetsu allowed him to use his Mokuton. After his assault, he then began to train his abilities. He can't use Mokuton ninjutsu, as he is not entirely Senju DNA. Being entirely Senju DNA is required to use the Jutsu(Yamato). Yamato was worked on as an infant by Orochimaru, and was the only child found compatible with the First's cells. Which is why he's currently the only living person capable of Mokuton Ninjutsu. If you are not entirely Hashi cells, and try to use the abilities too much, you become unstable. Such as Danzo. He used the abilies to an extreme extent and the DNA soon took him over. He wasn't compatible with it. That's what would happen to Obito if he tries to use the DNA too much. That's why he barely uses it, and when he does, it's in small amounts.
The only difference between Zetsu Mokuton and Hashi DNA Mokuton is, if you are entirely Hashi cells(Yamato), you can use the jutsu. If you have Zetsu on you, you can use the abilities(Such as Obito killing the Mist ninja). If you merely have the DNA on you, or in parts of your body, you can use the abilities, but over use will make you unstable(Danzo).