In particular, when making an Organization coat, we actually sew a "decorative" top stitch in the garment vinyl down the front opening before placing the zipper in. We then pin the zip in place (with as many pins as possible...the more pins, the less possibility for wobbly stitch lines), pushing pins horizontally only along the pre-stitched line, so as to avoid extra holes in the vinyl.
Alternatively to pining, the entire zipper -can- be Liquid-Stitched bit by bit to each edge, WITH PRESSURE then applied to the top (a book placed overnight is more than sufficient - but Liquid Stitch needs to be pressed flat as it dries.) This is to keep the zipper even on both sides as the fabric adhesive sets. The bond, once set properly, is permanent but still flexible - however, to be extra safe, stitching once more over the previously only-decorative stitch is advisable - and because the zipper has already been securely flatly with the glue, the garment vinyl doesn't become puckered or wobbly. That last sewing stage is good security so the zipper can be yanked opened and closed often.
When working with a zipper that has been hand-fused: remember that the spliced zipper should not be unnecessarily zipped before or after being secured to the garment, and high-stress bending should be avoided. Spliced zips are for occasional costume use only, and we recommend only attaching to fabric that is at least medium thick and with a slight give (such as with SYFabric's garment vinyl or real leather.) Anything that is too tight or does not stretch enough perpendicularly to the zip may cause the teeth to split on the splice. In addition, be wary when making tight-fitting coats, and be various honest with your measurements, taking also into consideration of how you bend when sitting. Also, if you choose to machine-sew in a combined zipper, do not sew where the small triply-thick spliced area is (which would break a needle.)
For any zipper used only as a decorative trim in areas that won't ever be zipped, Liquid Stitch applied inside the hem seam is more than adequate, and top-stitching is not necessary.