ZTA is a cancelled open world action game that was in development by french studio SDP Games (Smack Down Productions) for Sony PSP. As you can imagine from its name, the game was meant to be a clone of GTA, but focused on the zombie apocalypse. This lost game was revealed some years ago by a French website, with a few details directly from the developers. It seems SDP Games tried to pitch their project to Rockstar Games, but without any luck.
As we can read from the original article (“translated” with Google Translate):
“This is our very first game prototype! It was indeed a GTA with Zombies on PSP, very zany with the music of Weird Al. We were in contact with Rockstar for the edition, but we never could agree on a budget. Unable to find another publisher, we had to abandon it to move to Nintendo DS ”
Only a bunch of screenshots from the ZTA prototype survive today after the closure of the studio, preserved below to remember the existence of this lost game.