What's the difference?

Coke zero actually almost tastes like Coke. Diet Coke has its own flavor profile.

One is marketed at men using sports celebs, the other is marketed at women. Men don't like to think they're on diets.

Zero definitely tastes different. What's really odd is that I know "diet coke" as "coke light". But "zero" appears to be world wide.

Also here in Australia we now have Coke (Zero sugar ) as a seperate new drink like wth

Diet coke uses artificial sweeteners and Coke Zero uses stevia

Aside from the marketing, I think the sweetener they use is different, but the big difference is the caffeine content.
Coke zero has the same amount as regular coke. Diet coke has about 50% more. I can't remember the exact numbers, but they're written on the bottle/can near the nutrition facts

Both will strip rust and give me a week long migraine.

Both are fucking advertising lies.