Agreed on zero being better than diet. They actually use the same sweeteners, but a different flavor profile.

FWIW, in the US at least, Pepsi Max also became Pepsi Zero.

I suspect both are getting away from the 'diet' moniker because of the fact that people not on an active weight loss diet prefer them, ruining the played out joke of 'haha he ordered 2 burgers and a diet coke.'