I don't like diet coke either, but think that Zero is completely different. Make sure you drink it when it's cold. My impression is that it also depends on the type of artificial sweetener used, which depends on local taste and regulation. I think it tastes good in Europe and most parts of Asia.
I drink primarily Zero, I switched to it at the same time I ditched sugar in favour of artificial sweeteners (I tried to drink tea without any sweetening but gave up after few weeks, I just can't stand it). It's wonderful where I live (Poland), and I grew to like it even more than plain Cola. I've also seen numerous attempts to promote Zero over the original flavour; one time they even gave away cans of Zero disguised as ordinary Coke to make a point (you had to remove the can from a cardboard overlay it was in to discover it's Zero). I don't know how successful were those campaigns though.
It's funny because I think Zero (and original) taste absolutely disgusting and make me feel sick within minutes of drinking them. But I do have a severe weakness for diet coke (aspartame). I've mostly eradicated diet coke over the last year and now I just drink water or black coffee. Water wasn't so hard a transition really, but developing a taste for black coffee took a few months of dedication.
