Sew the shorter, front top edge to the back of the lower lip and to the lower half of the zip.
Sew the longer, back top edge to the back of the upper lip and to the upper half of the zip.
Leave enough space between the edge of the fabric and the working parts of the zip that nothing catches.
You may need to play about and do some extra stitching inside the mouth to prevent the satin catching when the zip is pulled, to seal the top edges of the bag firmly to the sturdy fabric of the zip (I recommend tiny hemming stitch in a thread matching either the bag or the zip), and to close up any gaps around the outer mouth area. Don’t be afraid to improvise and stick a few extra stitches where they’re needed. A working mouth is more important than perfect stitching.