HID conversion kits (an HID bulb with a high voltage power unit or ‘ballast’ which fits into the original headlamp unit in place of the original bulb with no change to the headlamp lens, reflector or housing) are illegal on any vehicle being used on New Zealand roads.
However, a complete halogen headlamp unit can be replaced with a complete HID headlamp unit provided that the replacement headlamp unit complies with approved standards. If in doubt, get advice from a vehicle lighting retailer you trust.