Patagonia outerwear that keeps you warm on brisk days and dry on wet days. Repair difficulty ranges from simple tear patching to more complicated baffle repair.
There are several adhesives suitable for fabric such as Loctite vinyl, fabric & plastic; E6000; Sew No More; or, Patch Attach which you might use. You might try taking two stiff wooden slats slightly longer than the length of the separation and two or (better) three clamps and, with the zipper open, spread a small amount of your chosen adhesive on the portion of the zipper that you want to adhere to the fabric (you don't want to put on so much adhesive that it squeezes out when you clamp it), put a wood slat on each side and clamp it all together. You can probably get away with using spring loaded squeeze clamps but you can use whatever clamps you have on hand.
Oh, and if there is any old adhesive remaining on the separated area, you would want to do the best you can to remove it before making the repair. It's not obvious from your picture what kind of material you're working with so I hesitate to recommend a solvent. My go-to is acetone but I would be very cautious and try a tiny amount applied by the corner of a dried out alcohol pad. A product called Goo-Gone is probably safer than acetone and is also very good at removing adhesives.
@logandunn Can you upload a picture of the problem? Adding images to an existing question
crwdns2934271:0crwdnd2934271:0 Andrew S crwdne2934271:0
I updated the original post to have the picture in it
crwdns2934271:0crwdnd2934271:0 Logan Dunn crwdne2934271:0