You can drive Ezi Car Rental cars on any road except ones not part of normal touring routes. You will not be insured if you drive on the following roads:
Tasman Valley Road - also known as the Ball Hut access road (Aoraki/Mt Cook)
Skippers Canyon Road (Queenstown)
Ninety Mile Beach (Northland) ninety mile beach Skippers any roads
Any roads north of Colville on the Coromandel Peninsula