class Zip(models.Model):
    category = models.ForeignKey(Category,null=True,verbose_name='Категория')
class Attachment(models.Model):
    zip = models.ForeignKey(Zip, verbose_name=_('Zip'))
    file = models.FileField(_('Attachment'), upload_to=get_upload_file_name)

 class ZipForm(ModelForm):
    class Meta:
        model = Zip
     #   model.subcategory
        fields = ('__all__')
        exclude = ['user','creation_date']
    files = MultiFileField(min_num=1, max_num=3, max_file_size=3024*3024*5)
    def save(self, commit=True):
        instance = super(ZipForm, self).save(commit)
        for each in self.cleaned_data['files']:
            Attachment.objects.create(file=each, zip=instance)