Zara event dress size small

beautiful goddess dress. its a fine find from zara. its been in my closet far too long in hopes that i can fit in it again. its not happening:( worn to a wedding once and received so many compliments. its classy, modest and mysterious. im size 6 and cant zip back up completely. so ladies size 4 or S would be the best. enough space in chest area. i didnt feel constricted. its a suit material. has breen dry cleaned. hate to see it go :( feels like a good quality. perfect condition.