Hot Tub Cover Depot

The hot tub cover arrives in pieces, and must be assembled. The foam pieces don't fit inside the cover, even after heating it up to 90* to soften it. I had to destroy the foam to get it in. Because of this poor fit, there's lots of strain on the zipper, which broke immediately because it's brittle zinc. Customer service was useless. I'm left without a hot tub cover, and without $500.

Here's my exchange with Customer service:
Me: "I tried to in the foam pieces and zip it up, the pull tab on the zipper on the vinyl broke. When I put some twine through the zipper area where the pull tab broke off, the ensure zipper thing that combines the zipper broke off. Please help, this has been very frustrating"
CS: " Sorry you are frustrated. As the instructions from the vinyl box explain, you cannot use the zipper to force close the vinyl...we test assemble every cover before we package it to insure it will assemble easily for our customers.If you will ship the vinyl back to us, we will repair or replace the zipper, and return it to you."
Me: "If there's a note about that in the instructions (*note, there isn't), it's not where I could find it (see attached). Will you send a label, or am I expected to pay for shipping?"
CS: "Customers would be responsible for shipping."