It replaces the word jackass with a word that no one knows. Jay Z said it on his album, so I would tend to believe it means a Black person. We have converted it to mean anything or anyone. You could be black, white, jewish, indian, mexican, spanish, etc. It doesn't matter who you are, your still a jzenna. It is also a word for someone who has more then you do.
Whats up you smelly Jzenna? Hey jzenna, you seen my lighter? Your a fucking Jzenna. Don't be a fuckin jzenna you smelly jzenna. What's up jzenna, what chu doing. That guy is a jzenna.