Originally Posted by
Globaliser
I think they're registered in New Zealand (ZK- registrations) rather than Australia (VH- registrations) so that they can easily be operated by a NZ airline (Jetconnect/QNZ). It's possible for aircraft to be repeatedly de-registered and re-registered in different countries (eg the Braniff tag for Concorde flights from IAD to DFW) - but it's a faff, so it's unsurprising that Jetconnect has a dedicated fleet.
JQ NZ uses Australian (VH) aircraft, no need to register to ZK to operate within NZ, and possibly able to fly ZK aircraft within NZ, the recently defunct Vincent Aviation Australia seemed to use ZK aircraft from Vincent Aviation New Zealand.