What are some alternatives?
When comparing DayZ and 7 Days to Die, you can also consider the following products
Evolve - Evolve is a desktop app and community for serious gamers.
Rust Game - Rust’s world is harsh. The environment is not kind. Bears and wolves will chase and kill you. Falling from a height will kill you. Being exposed to radiation for an extended period will kill you. Starving will kill you. Being cold will kill you.
Unturned - You're a survivor in the zombie infested ruins of society, and must work with your friends and forge alliances to remain among the living.
Dying Light - Dying Light is an Action-Adventure, First-person Perspective, Horror-Survival, Zombie, Co-op, Role-playing, Single and Multiplayer video game created by Techland and published by Warner Bros.
Left 4 Dead - Left 4 Dead is an Engaging, Action-Adventure, Horror-Survival, FPS (First-person Shooter), Co-op, Single and Multiplayer video game created and published by Valve.
Project Zomboid - The Ultimate Zombie Survival RPG.