Complex sentence: New Zealand purchased 5 SH-2G at the same time as Australia, but with different avionics, and the New Zealand aircraft were new-build airframes, not rebuilt American SH-2Fs.
Split into simpler sentences: New Zealand purchased 5 SH-2Gs at the same time as Australia, but with different avionics. The New Zealand aircraft were new-build airframes, not rebuilt American SH-2Fs.