You need exact measurements otherwise it won't fit.
If you want a zipper along three sides it is easier to do that the traditional way, although it can be done.

I measure and add 5 mm (or about 1/4 inch) to get a nice outline.
Embroider outline;
place front fabric first and pin;
embroider design of your choice;
then pin the zipper along the outline, cutting the band almost to the teeth in the corners, use tape to secure, stitch the outline again;
place the two inside panels and the lining (width half an inch shorter than the outline, height covering it nicely) stitch the final outline and turn.
Job done.