Husqvarna Viking Clear Invisible Zipper Foot

Invisible Zippers (sometimes called concealed zippers) are most often seen
in the center back of a dress, in the side or back of pants and skirts, and in
some home dec projects.

As the name implies, the zipper is hidden in a seam, becoming virtually invisible.
This zipper application is often thought of as very difficult to do, however it’s
really one of the easiest.