Coca-Cola Zero is a product of the Coca-Cola company, released in June 2005. It is a sugar-free variation of Coca-Cola Classic, sweetened with a blend of aspartame and acesulfame potassium. This product is different from Diet Coke because of the sweeteners it uses (Diet Coke only uses aspartame), and because, unlike Diet Coke, this product is based on the original Coca-Cola formula. Diet Coke was an entirely new formula which would eventually become the basis for the controversial New Coke (later renamed Coke II).
Contrary to popular belief, Coca-Cola Zero is not a new formulation. The same blend of aspartame and acesulfame potassium along with the Coca-Cola Classic formula has been available for quite some time in many European countries which were never exposed to New Coke. Commonly called Coca-Cola Light or Coke Light in Europe, the Coca-Cola Zero formula is identical to that used in foreign countries.
http://en.wikipedia.org/wiki/Coke_Zero