Alien Year Zero was the in-development title for Alien: Isolation.
The developers, The Creative Assembly, were believed to have officially started hiring for the project in 2011 after beginning work in 2008. The game finally released in 2014 on Xbox 360, Xbox One, PS3, PS4 and PC.
Alien Year Zero (or AYZ) was a title seen most publicly from employees of Axis Animation while developing the CG Trailer for Alien: Isolation, and can also be found within the Steam Database for the depot and package names of the game. The beta of Alien: Isolation is named "AYZ Beta" and the early access package of the game is named "AYZ Early Access Comp".
It is not known how long the name stuck for, why it was changed, or if it was just a working title to keep the official title secret. The game's animations typically begin with the prefix of "AYZ" so it is possible that the name was kept for a large period of the development cycle.
The trademark for "Alien: Isolation" was filed on the 17th of October 2013, with no trademark being filed for "Alien Year Zero".