IMO I would go with what the others have said, control your right foot properly and that will save you most fuel. Get it into higher gears ASAP and dont rev it hard (equally dont let the engine labour). If you're not so good with the right foot then get a throttle controller and set it to Eco.
Really though, its an NA car, you're never going to be able to detune it for much more economy, you just have to live with it. If you dont rag it the Zed is suppringly frugal for a 3.5l engine