unusedzips.py

from teams.models import Team
from zipcodes.models import ZipCode, County

Z = list(ZipCode.objects.all())

for team in Team.objects.all():
    for zip_code in team.zip_codes.all():
        if zip_code in Z:
            Z.remove(zip_code)
    for county in team.counties.all():
        for zip_code in county.zip_codes():
            if zip_code in Z:
                Z.remove(zip_code)

import pprint
pprint.pprint(Z)
print len(Z)