Best of luck to it (no irony!). That said, it might not hold. Stamping out the virus (2) requires keeping a perimeter around all existing carriers. New Zealand, being naturally removed from other countries, has some advantages in this regard. But even there, as soon as travel restarts reintroduction is not unlikely. We will see...

For example, many countries kept mandatory smallpox vaccinations long after the disease was eradicated within their borders because otherwise a single traveler can wreak havoc. Check for example smallpox reintroduction to Yugoslavia in 1972 by a single pilgrim. A quick martial law and quarantines helped contain it, but even then it caused, according to Wikipedia, 175 infections and 35 deaths.

If COVID-19 is as virulent as it is claimed to be I would not bet on NZ staying COVID-free after travel restarts. My 2c.