I could not tell you why, but I have been very intimidated by zippers my whole sewing life. I have attempted them, and just never had real success. They worked but looked awful. I guess where i went wrong was trying to do it with out any instruction... well, I got some amazing fabric that i wanted to make a pillow with, but it was a zipper pillow that was speaking to me :)
I found this tutorial on Design Sponge to be super easy to follow, and the results were great. If you have a phobia of zippers i highly suggest facing your fears with this tutorial.