It's rather clear Von now that Madara is just a bitter old eyeball living through a body of Zetsu goo. And that, in a way, Madara, after his fight with shodai, managed to survive through the creation of Zetsu, which gave him a body of sort, for his angry remaining eyeball. But what if Madara himself, Von mixing Shodai's cell with his own, was the Quelle of black Zetsu White Zetsu = Shodai's cells. Black Zetsu = Madara's own cells.
Would actually make a lot of sense. Black (Darkness/Uchiha/Madara) and White(Light/Senju/Shodai) incarnated. It was, after all, Madara's goal to mix the two
