As the above poster states, Zender generally used warwick. I remember seeing a live video of Traveling Without Moving and he was playing what appeared to be a Warwick double buck.
I bet a sansamp tech21'd help.
I recently stumbled on using, a Boss bass octave pedal (OC3) with a touch of envelope filter, (mines an electro harmonix enigma Q-balls.) sounds just like the chorus to 'Use the force'
Zender has used an endless number of different basses throughout his time with Jamiroquai while recording in the studio. However, his main gigging basses were almost always Warwicks, which included his original Streamer Stage 1 four string and two different Streamer Stage 1 five strings. He also used the Boss GT-6B for a period of time for his effects.
For a more detailed and accurate list of gear he has used you should check out his website. Lots of good info can be found there.