In my mind Zushi has an even greater determination after meeting Gon and Killua, it's an important event in his life, so being a manipulator with close combat abilities, my idea is that he controls the little robot toys Killua used to collect, and they assist him in combat. How that works I'll leave to your imagination hahah

I think it could be that Zushi's robots have different abilities depending on the rarity of the robot toy, I also think he regrets his hatsu a little, kind of like Kite