Of course, zero covid everywhere! Just need a co-ordinated, simultaneous worldwide lockdown, no worries! Never mind that people living hand to mouth will die of thirst or starvation, no police, no doctors, no hospitals, no food deliveries, you get the idea. Seems entirely achievable!
Erm... Slightly hyperbolic!
The only country that totally shut borders and stopped all imports is North Korea.
NZ and others who employed temporary - and what could've been (had everywhere done the same) very short-term pandemic border controls (control, not full closure) still imported necessary food, medicine, etc.
The fact of them having a quarantine system is evidence of the fact of not completely closed borders.
The same principle applied for essential jobs.