Rotorua for a couple of days but gets samey after that
Wellington for lots of varied trails in and around a vibrant city
Nelson/ malborough area: whites bay, wakamarina, nydia track, fringe hill, 491, dun mtn, rameka and killdevil. Caveats, some of these are back country and technical
Chch: ports hills for a day, double de Céline, wharfedale track and craigiburn
Wanaka and Queenstown as others mention
Don’t underestimate driving time
Have fun