Where is Orochimaru? Why isn't Orochimaru releasing the Edo Tensei seal of Hashirama?

Wouldn't that be helpful, as Madara would no longer be able to use his Senjutsu chakra?
Madara has obtained the cells of Hashirama and has them infused into his body, irrespective of what happens to Edo tensei hashirama it will not affect anything with respect to Madara because he has been revived using the rinne tensei technique of six paths.

In short madara has both powers of Senju and Uciha and on top of that he is completely by himself (unlike being under Kabuto's control briefly when he was revived).