Is it permissible to put a zip on any part of a woman’s wear; on the back, the side, or on the chest?.
Praise be to Allaah.
There is nothing wrong with putting a zipper on a woman’s dress, and there is no limit to where it may be placed on the dress. It depends on where you think is best for it and what is concealing. End quote.
Fataawa al-Lajnah al-Daa’imah li’l-Buhooth al-‘Ilmiyyah wa’l-Ifta 24/36.