From what i've read zelnite is good for nearly everything. He's as good as felneus for gaining bb's, but also increases hc's significantly so he heals a decent amount. He has really solid rounded stats too. Then you have increased zel/karma/item drop as a bonus on top of that. I'd pick him over uda/other bb leaders as the bonus healing on top of everything else seems nice to have in a harder situation. Some bossfights you're using a strict leader combo so you wont use zelnite, or you'll be running maxwell but i think zelnites best in leader for most of the stuff your doing.
He's also meant to be a really good arena leader- I can imagine having him at the top of your arena team and his bb going off and filling some of the lower down units bb will be sweet.
He's also meant to be a really good arena leader- I can imagine having him at the top of your arena team and his bb going off and filling some of the lower down units bb will be sweet.