Mine did the same so I did this.
1. Make sure ur unzipping from right to left
2. Remove the bottom part like normal
3. Straighten the zipper as much as possible
4. Try to unzip it.
If that doesn't work force it or go to a Jeep dealer ship.
Grab your sense of adventure. Leave the rest behind.
mine is a YJ, a little older but still plastic zippers. They make stuff called zipper-eaze or something like it that I've heard works? I was also told that candle wax rubbed on the zippers will help to. Personally, I would always use a pair of plyers to pull my zippers, they were always way to hard on my hands. I'm just a skinny guy, not to much muscle in my long fingers! Plyers were a must.
For me it's always been good old fashioned elbow grease... I only paid $75 for my soft top so it wouldnt break my heart if I damaged it... I am saving up for a hard top anyway... I am tired of the noise and figure I can do well enough with the back window open and the doors off.
Losing hours at work? Taxes up on your paycheck? Having trouble finding a doctor? Your kids trashy?