Board Thread:Naruto Discussions/@comment-1512913-20170417105433/@comment-734582-20170418055510

Namikazenaruto9 wrote: why is that? Madara could do it, obito too. Danzo had the cells and couldn't. The zetsu had the cells and couldn't.

But like i said, Kabuto probably used Zetsu cells, and we've seen that they are much weaker with wood release while still possessing considerable healing capacity. There could be multiple reasons for this, but it's possible Kabuto had no access to Hashirama cells after Orochimaru died (or Orochimaru no longer had access after he left the village). It could explain why he was so eager to work on Zetsu and "improving them" despite no apparent change.