I had the same problem with my Ameristep blinds here in Michigan. I contacted Ameristep in Clio Michigan about putting little flaps over the zippers to prevent the problem. They basically gave me the finger and said they were pop up blinds designed to be transported out in the morning and back in the evening. I took one to a canvas shop with some camo cloth strips and they sewed them in place to keep snow and freezing rain out of the zippers. Since I had it done after the fact at a canvas shop It cost me $35.00 for the cloth and sewing labor. Told Ameristep I would never recommend there blinds to any one for fall winter hunting I am sure they could do the cloth strips over the zipper for less than $10.00 per blind done at the factory.
I don't know of
any company that really cares about their customers and put a cover over the zippers.
Al