I said I would take these but I wanted an invoice from Paypal. What is the problem with doing this? I see that you are a new poster on this site. This might be a scam then.
Try spraying the whole area with WD40. Let it sit for a while and then try pulling the thread out. If you get it out, repeat the WE40 and let machine run a while. You may have some other thread in there that you can't see.
One side of the zipper stays on the leaders all the time. My set of zippers has 3 zippers. So you could unzip the quilt and put another on to work. I only used two (take up leader and backing).
The zippers separate so one side of the zipper is sewn to your leader and it stays there. You attach the other part of the zipper to your backing and zip the two parts together. I hope this makes sense. I have a set of 3 for a 14 foot table that I would sell since I only use a system like Red Snappers now.