Not sure if that quote is 100% accurate but. I am getting tired of seeing white zetsu is the man in front of Sasuke because of this panel. http://www.mangapanda.com/naruto/661/17
Lets make it clear to all, that quote, was Madara speaking in context of what he was talking about to Tobirama. As you see Tobirama later addresses what Madara means by the treatment, and Madara confirms he indeed wants to put everyone under the infinite tsukiyomi
White Zetsu then later on appeared to where spiral zetsu was, that is where zetsu intended to go when he said "ill head out right away!"
Nothing from that quote has anything to do with Zetsu going to heal Sasuke. Besides Sasuke was on top of the Gedo Mazo with Madara and Tobirama and white zetsu disappeared elsewhere to spiral zetsu. If he was going to heal Sasuke he would not have gone anywhere. It's either Kabuto or a new character as for who is inside of spiral zetsu it's either Yamato or a new character.