Earlier quoted context omitted.
Diet Coke uses aspartame also. I figured the difference between Coke Zero and Diet Coke was branding for people who don't want to drink something labeled as diet. EDIT: I drink both regularly (including today), and I personally do not perceive difference in taste. YMMV.
Coke Light => Women Coke Zero => Men
Not saying any of this is a good thing... but it's a thing.