then again this is an edo tensei with sacrifices like the one used in the konoha invasion, where oro took control over the minds of the kages after that they started alerting the thirds about their attacks... i am not sure if kabuto used zetsus to use the mass summon and kabuto didnt took control over the minds of the dead

also edo tensei doesnt override the Shiki Fuujin seal, oro sacrificed his own body to let the 4 spirits out of the shinigami's stomach along with the half spirit of oro that was sealed, then summoned the kages sacrificing 4 zetsus and at the moment that oro's body was about to perish he transferred himself to the 5th zetsu, leaving one last living zetsu, 4 kages and a new body with hashirama's cell(expect a new power up coming) for oro