Manga Spoiler Alert
In the latest manga chapter (677), Madara successfully initiated the Infinite Tsukuyomi.
However, Tobirama Senju seems to be unaffected by this. Why is that?
Given the fact that none of the Edo Tensei'd Hokages were affected, I'm guessing that Edo Tensei reanimated people are not affected by it.
There wasn't much said about it anyway, but that's the option that makes most sense.
I agree with Madara Uchicha's answer, the dead (Edo Tensei'd) characters don't have original chakra for the God Tree, so the the tree does not attempt to absorb them?
Maybe the Hokages will help Naruto and Sasuke attack Madara.
It seems to me the God Tree and Infinite Tsukuyomi targets bodies with life force and chakra. Edo Tensei shinobi possesses infinite chakra, but not any life force, which is insufficient to fall under the genjutsu.
Beyond this, Kishimoto has never shown any Edo Tensei falling under genjutsu. Furthermore, when Sasuke (from Sasuke Retsuden) tries to put Meno (an Edo Tensei dragon) in a genjutsu, it doesn't work.