sign, symptom, or diagnosis, it is appropriate to assign both the V code and the code describing the reason for the non-routine test. 18
The difference is in the types of non -nutritive sweeteners used. Diet Coke has aspartame while Coke Zero has a mix of aspartame and acesulfame potassium. The beverages have different levels of sweetness and off tastes (I.e. high levels of aspartame have a metallic taste) as a result.
Coke Zero is made by the Coca Cola division, and designed to taste as close to regular Coke as possible -- not marketed as diet but as zero calorie and sweetened with Ace K & Nutrasweet.