Apply a lighter directly under the zipper for brief periods at a time, to let the plastic melt slightly so you can pull it back and remove it? Also, directly melt any portion of the plastic bag showing>

My concern about using a lighter is that this is a cloth duffle bag... I don't want to burn it.

Hrm. Depends on exactly how it's caught, but often simply size-sixteening it can be a solution. If you've already tried size-sixteening it, or getting someone else to do the same, then you might start down the playing-with-fire route. Just be *very* carefull and bring the flame *slowly* closer to the plastic - if you just flick open a bic and apply it to the plastic, you'll probably scorch your duffle bag and get plastic goo permenantly stuck to it.

Size Sixteening means "Apply as much force as possible." It originates from the thought of "If kicking it doesnt work, find someone with a bigger foot." Size Sixteen being a VERY BIG shoe size.

It depends on the zipper, though. If it is a duffel bag, it probably has a big heavy-duty zipper, and that means that forcing it probably won't hurt it.

As far as being worried about scorching the fabric - a reasonable concern. This is why I mention not touching the flame to the plastic bag - just bringing the heat close to the plastic bag should make it shrivel up a bit, weaken it enough for you to force the zipper. You could probably also do it with a hair drier.

Do it *with someone else*. While you (or they) apply the heat to the plastic bag area, the other person is wearing gloves (just in case) and have a hold on the zipper.