The picture is a little difficult to see, but Zell wears his hair spiked up with some inordinate amount of hair gel. He dons a thick black tribal tattoo on the left side of his face, and he is almost constantly wearing a great big grin, which can be perceived as cocky. Right off the bat, people would get the wrong idea about him.
Then when it comes to his clothing, it only makes it worse. He wears baggy cut-off jeans and a muscle shirt beneath a cropped jacket with his sleeves rolled back so he can punch someone in the face more efficiently. He looks like the stereotype of a '90s North American hooligan, not going to lie xD Even in-game NPCs judge him for it. As far as design aesthetics, probably not the way I'd go, but it all works in Zell's favor somehow. I just can't imagine him all donned in badass leather like Squall, cowboy clothes like Irvine, or being a trench coat extraordinare like Seifer. His clothing design? Yeah, kind of lame. Does it work? Somehow, hell yes.