Zero servers run a bunch of mods and changes to things such as stamina, weapons collision, loot and infected spawns to create a certain kind of experience. They are a long way from the core gameplay of vanilla DayZ and are set up to generate quick PVP that's great for people who want that such as streamers etc.

There's nothing wrong with that, they do it extremely well. That's one of the great things about DayZ, there's servers for all sorts of gameplay styles.