This function already exists as an efficient custom ModelManager method called `by_zone` -- see `SyncedModelManager`. It can be called for any SyncedModel. The advantage of custom ModelManager methods is that they can be chained together in a query, e.g.:
`Device.objects.filter(name__startswith="Test").by_zone(zone)` or `Facility.objects.by_zone(zone).order_by("name")`