From Hertz NZ
At time of rental, the renter must present a full valid driver’s
licence issued from their country of residence that has been held for
a minimum of one year. If the licence is not in English, then an
International Driver’s Licence is also required.
New Zealand law requires you to carry your driver’s licence with you whenever you are
Renters from China can use a China Notarial Certificate
(CNC) which is used in place of an International Driving Permit,
however their original Chinese licence MUST accompany the driver as
well as the CNC.
Sadly the page was dynamic but i found the information through the following method:
Reservations -> Qualifications & Requirements -> EnterAiportCode:"AKL" -> ChoseTopic:"Drivers Liscence" -> Go
NZTA (New Zealand Transport Association)
*A current and valid overseas driver licence means that your licence allows you to legally drive in your own country. If you are
disqualified from driving or your licence is currently suspended,
expired or revoked, then you are not allowed to drive in New Zealand.)
The Keyword there is "valid" my understanding is it is not a valid licence without both parts. However find information from the DVLA on this matter is tricky.
The New Zealand Police has the same statement as both the NZTA and Hertz.