Wait a minute... White Zetsu is of Hashirama ... Black Zetsu is of Madara... that makes the whole Zetsu one part Senju... one part Uchiha...
O. M. G.
ZETSU IS THE REINCARNATION OF THE SAGE OF THE SIX PATHS!!!! It all makes sense now...
A simple souvenir of someone's kill
And like the sea
I'm constantly changing from calm to ill
Madness fills my heart and soul as if the great divide could swallow me whole
oh, how I'm breaking down