I´ve fixed lots of zippers, and broken a few ones, here´s what you may try but I take no responsability if you break it, try at your own risk:
Take the pulls all the way to one end where they used to separate, I'll assume it´s the bottom, look at the sides of the pulls, there should be a slot along each side of the part that holds the teeth, it´s like two parts held together at the middle, the cross section is an "H" shape.
What you have to do is open a little bit the side of the pull where the zipper used to separate and take that zipper half out the side, you have to be gentle because the pulls break easily, in most pulls you can open one side a bit by pressing the other side very gently, sometimes it can be done by finger pressure, sometimes you need pliers, it´s like getting the front and back parts together so that the opposite parts separate, they only have to open up a very little bit, you then pull one side out starting at the top of the pull, get the slot in between two teeth and slide it out.
I f you manage to get it out, check the pulls to be sure that they are in good shape, generaly they are fine, but if they are assymetrical you may have to press very gently on the side that is opened more, if they are not right the zipper will likely get out of the pulls when it shouldn´t.
Here in Mexico city there are places that sell spare pulls in diferent sizes so if one breaks I can get a new pull, they are easier to put in than to get out, I don´t know about the U.S. or Canada.
I hope my explanaition is more or less clear and wish you good luck.