As much as this is gonna hurt to do, chop the car into two, piss the rear half off (after you pull out the LSD I guess), ship the front half to oz. In WA, find a car that's got an almost dead engine or soemthing, get the rego on it (mail it in), then swap the engine and all the parts over from the half cut.
Probably the easiest way to get most of your old car on the road in oz. You'll make some cash back on the panels from the old car in NZ, and maybe some cash from the parts you pull out of the car in WA. Probably not much tho.