Principle like, execution zipper improvement

I use the insect repellent is not mobile, but just over my bed at home. The tent-principle I like much better than fixed on the ceiling grids. However, I have to fight so that the zipper so far goes down. If you look at the picture closely, you can actually see what my problem is: the lower horizontal part of the zipper is located between the bed frame and mattress. This enables not particularly convenient opening / closing the zipper.
This, however, that there are 2 Zipper, I can at least vertically pull the zipper well, and the rest I put between the mattress and bed frame.