Why is it important what zone I live in?

Because the zone you live in affects the distance that a frost fan can be installed without requiring a resource consent.
If you live in a 'Rural' zone that distance is 100 meters.
If you live in a 'Residential' zone the distance is 500 meters.
Now this will differ from district to district, because each has to make its own rules. The have to make sure those rules comply with the Resource Management Act.
The rules above are relevant to the Marlborough District Council's Proposed Wairau Awatere Resource Management Plan (It says proposed, but it's the one they use (more legal beagle machinations that can be ignored in this case).

Not it gets tricky.
To make matters more difficult there are a multitude of different zones. including 'Rural Residential'. The levels of grey can sometimes appear never ending.

The basics are still the 500 meter and 100 meter rule (in Marlborough).

Let's not forget that there are other standards that they must also meet before they can be installed! But I will have to save that for another post...