How did Madara come to learn "said" sealing techniques? Hashirama learned powerful sealing techniques because his wife was of the Uzumaki clan. The Uchihas however, have no such relation.
Why can't the black Zetsu activate a sharigan like Madara? The white Zetsu has plant like abilities that seem to stem off of wood jutsus, but the black one doesn't seem to have inherited any Uchiha-like abilities.
If both Zetsus are combined together, why can't they just activate Izanagi like Danzo/Madara? It would've helped at the Hokage summit if they were able to.
The black zetsu is as everyone theorizes, made from an Uchiha. If we assume that the coffin that Kabuchimaru summoned through Edo Tensei is really the real Madara then it would make sense, but how would it have come about? And what created the current "Madara/Tobi" in the first place to be able to create a black zetsu further down?