Coke Zero, Coke Lite, etc, all contain artificial sweeteners, ALL of such (eg. aspartame, saccharin, sucralose, acesulfame K, neotame, etc) are even more harmful than sugar, and have been shown to increase the risk of cancer, diabetes (the irony), high blood pressure, kidney failure, stroke, etc.
Coke, in moderate amounts, is healthier than any amount of Coke Zero, Coke Lite, etc. But if you're addicted to the fizziness of drinks and drink way too much coke or soft drinks, then I recommend you drink cut down on coke/soft drinks and replace (at least half or more of) your drinks with Perrier, which is naturally carbonated (ie. fizzy!) mineral water.
One health advantage of Perrier over tap water, is that it contains way less harmful fluorides (google about the harmfulness of fluoridated tap water). And because it doesn't contain any sugar, it's healthier than coke and all other soft drinks. And it tastes great and refreshing, because it's naturally carbonated (ie. fizzy!) mineral water.