Zippers that extend from the top, all the way down to the bottom of a dress back are. not. fashionable.  They do not make you seem alluring or mysterious.  They don't draw the eye to a flattering area of the body.  In no way do they say, 'I'm a lady out for a night of good clean fun.' They are brash, awkward, and could easily lead to an accidental mooning situation.  That zipper dress does not say classy cocktail. It says, hi, I'm a hooker.