zipper novice.

[closeto-me.livejournal.com]

I've been working on reconstructing one of my old a-line skirts into a high-waisted pencil skirt, which requires me to have to fiddle with a zipper for the first time. I used the zipper tutorial on whatthecraft.com to install the zipper, and when I put the skirt on, the zipper was puckered. 

Excuse the views of my backside, haha.

Can anyone tell me why this is happening and how I can fix it? I will be eternally grateful! :[