Zetsu has yet to be seen in battle but Madara refers to Zetsu as not being a 'front line' fighter. He already showed the ability to split in two, so that his two personalities can act independently.
He is also using time-delayed spore jutsu ability in order to grow into a mushy mass around several individuals at once.
So what do you think is he a powerful one????????(or are they powerful :D)