My understanding is that was what caused Zender to leave - the fact that the band's early efforts were largely collaborative, with many of the musicians actively contributing to the songs and overall sound of Jamiroquai. Then, when the record companies started dealing with Kay, he gave himself most of the songwriting credit and the rest of the band got BUPKIS (Yiddish for 'goat droppings').
Like I said, just my understanding, which, on any given day, is pretty much on par with my dog's. Oh well, it makes for a good story, anyway. Reminds me of the movie "Meatballs", they're telling ghost stories around a campfire and it comes down to The Big Finish: "and instead of his right hand... he had a metal... HOOK!" and Spaz says, "I heard the same thing, only it was his foot."
Yeah, there's my understanding, right there.