I've worked in both places. Once you have your license to practise in NZ, you can apply for Trans-Tasman Recognition in whatever state you'd like to work in Oz. You don't have to do one day's work in NZ to do this. You should listen to PhysioBob though, if you are going to go through all the time and effort to get an NZ license, you should take the time to use it. Also, some employers in Oz might be a little suspicious of a potential employee who appeared to get their license via a "back door" route.

If you haven't lived/worked in Oz or NZ previously, I can tell you from experience that NZ is a little easier to adjust to, and even a few months work there will go a long way towards enjoying your time in Oz (and likely getting a better job!).