I think it wouldn't be worth the effort or cost. Even with todays fuel prices I think you would have to be doing a lot of Klms to make it worthwhile. I looked into this for a different car a few years ago and back then it worked out with that car that I would have to do about 50,000 klms on lpg before I broke even, and this was with a car that there were premade lpg kits available for. With a Zed the install costs would be even higher I'd think. I'm not up on current lpg install costs.
Where will the tank go? - could possibly fit a donut tank where the spare currently sits - not sure what the regs in the UK or here in Aus are regarding placing an LPG tank in the cabin though.
I don't know if there would be enough room to fit a different LPG tank by removing the petrol tank and running 100% lpg.
It might be better to consider buying a cheap oiler as an everyday driver and keeping the Zed for Saturday and Funday
bollie7