Plenum spacer, better panel air filter, HFC's or De-Cats, full aftermarket exhaust system and then get the UpRev remap done is the way most people go for a little more power with the Zed.
Won't see massive gains but you will see an improvement in performance.
As Dan mentions though sometimes better tyres, suspension setup, brakes and driver training can in fact get you faster then you where before.
If you can I highly recommend the Ferodo DS2500 brake pads as they are a much better pad than those EBC green stuff pads you are currently running.
You could of course buy some cams for the Zed but honestly haven't read of anyone doing just cams alone, ...usually it's done on a built engine and then it does make a big difference overall especially if you are talking about an increased rev limit as well.