100% not the same thing. There is a really huge difference between them.
I can’t really tell who’s saying what here or comparing what to what.
Diet Mountain Dew and Mountain Dew Zero Sugar are utterly different products.
Pepsi Max has been renamed as Pepsi Zero Sugar. Those two are the same product. But it is/they are utterly different product(s) from Diet Pepsi.
Diet Sprite and Sprite Zero Sugar are again utterly different products.
IMO …
“Diet” is all about having that distinctive 1960s saccharine / 1980s aspartame tang. “Zero sugar” is all about having the exact same taste as the real sugar/HFCS-sweetened full calorie sodas. Insofar as 21st Century Weird Science! can pull that off.
Those are two utterly different goals aimed at utterly different target markets.
Diet Dr. Pepper & Cream Soda. I think it’s pretty new.
I don’t think DDP Cream Soda is even on their website
The link is from drpepper.com.
I bought a carton of it, and I like it.
diet pepsi used splenda for a short time. I guess sales went down so they went back to aspartame
Utterly different? They’re just sweetened differently, if that’s even the case. The sugarless Mt. Dew is one of my drinks of choice, and I can’t say I ever noticed a difference when the labeling changed.
I’m not so sure the labeling changes necessarily coincided with a change in formulation- I think Diet Sprite had already changed its formula by the time they renamed it, and the same with most of the others.
It’s been a hit or miss thing here for the last year, maybe not even that long. I really like it.
I know that Diet Coke has had a separate version which is sweetened with Splenda for several years – it’s a different product from their standard, sweetened with aspartame. I suspect that it’s not a good seller for them, either – while my local grocery store carries it, it has very little shelf space, and I wouldn’t be surprised if it gets discontinued at some point.
I remember a time – was it early 2000s , maybe late 90s-- where there were a good number of “Splenda” sodas. I remember seeing the Splenda logo all over the place. And then they quietly disappeared – that is, sucralose is still used in sweetening some/many beverages (often with Ace K), but I no longer see that branding.
nevermind
Poking around the internet (because I haven’t encountered MD Zero Sugar in the wild yet), it appears MDZS has fewer calories (zero vs. 20/500 ml bottle) and more caffeine (95 vs. 77 mg/500 ml bottle).
I actually kinda like Diet Mountain Dew, mainly because that sickly sweet taste reminds me of the original sickly sweet taste 
. Unlike most diet sodas back in the day it did a better job of imitating the original. But I’m confirmed Coke Zero drinker, so I’ll have to to give MDZS a try. That is a shit-ton of caffeine though - equivalent to a regular cup of coffee.
Dr. Pepper is far and away my favorite soft drink but Diet Dr. Pepper tastes so far removed from the non-diet version that I just can’t stand it.
I do like Coke Zero and the often hard-to-find Diet Rite.
Generally, in the US:
Diet = sweetness from aspartame.
Zero Sugar whatever = sweetness from acesulfame potassium, aka “Ace K” and likely some aspartame as well.
Some countries don’t use aspartame because of health concerns, but on the other hands many use sodium cyclamate that the FDA bans.
Pepsi Zero Sugar (formerly Pepsi Max, but still called the latter in some countries) has extra caffeine too, and ginseng.