In a Famitsu Interview, Yoshida, when asked on the weapon Zenos held, said that "while the weapons he hold doesn't really relate to his character." He then told the interviewer to look closely at his artwork later and see if they can notice something from it.



Take a gander at the 'sheath'

Here is my theory: The three weapons are, Wakazashi, Tanto and of course the Nodachi. Take a look at the length of the sheathes.

What would be the purpose? You know how MNK is able to execute certain abilities based on what stance they are in? I believe that should this reasoning be true, that the Samurai can execute certain abilities based on what weapon is in hand.

As Yoshi would agree, this is all speculation and I have no grounds to prove this true but, it's certainly exciting wouldn't you agree?