1. Introduction of the game:
Goat Simulator GoatZ is an offbeat expansion to the famously zany Goat Simulator, created by Coffee Stain Studios. This title fuses the absurdity of simulating a goat with chaotic zombie-survival gameplay. In GoatZ, players roam a post-apocalyptic world, causing mayhem, crafting items, and fending off hordes of zombies, all with a satirically twisted sense of humor.

2. All characters and levels of the game:
The primary character in GoatZ is the goat, which can be customized with a variety of outfits and accessories. Additional "characters" include a host of zombies and NPCs that add richness to the game's environment. There are two main modes in GoatZ - one focusing on survival with obligatory eating mechanics to stay alive, while the other allows for free exploration with no survival elements. There are several areas to explore, including a spooky farm, a carnival, and a town, each more bizarre and unpredictable than the last.

3. What attracts users most to the game:
The appeal of Goat Simulator GoatZ lies in its absurdity and the freedom it offers. Players delight in the anarchic world where the normal rules of games don’t apply, allowing for unpredictable and hilarious situations. The incorporation of zombies and survival elements into the already ridiculous Goat Simulator universe adds to the allure, especially for fans of parody and off-the-wall humor.

4. Why it is popular:
Goat Simulator GoatZ gained popularity through its unconventional approach to gaming, defying the seriousness of most simulation and zombie games. It offers a refreshing humor and self-awareness that resonates with players looking for an entertaining, stress-free gaming experience.

5. When the game was released and how many versions are currently available:
Goat Simulator GoatZ was released on May 7, 2015. It's an expansion of the original Goat Simulator game, and as such, it requires the base game to play. There is only one version of GoatZ, but the original Goat Simulator has multiple expansions and versions across different platforms.

6. The most difficult part of the game:
One of the most challenging parts of Goat Simulator GoatZ is maintaining the goat's health in survival mode. Players must consistently scavenge for food while fending off zombies and completing tasks, which can be difficult due to the purposely awkward controls and physics that often create chaotic situations.

7. Strengths and weaknesses of the game:
Strengths of Goat Simulator GoatZ include its humor, open-world exploration, creative gameplay mechanics, and the ability to cause rampant destruction without serious repercussions. Its weaknesses, as reported by some players, can be its repetitive nature, a variety of bugs (though some may argue that these bugs add to its charm), and a lack of depth in gameplay that might not appeal to players looking for a more traditional gaming experience.

8. What other games have been developed by the same developer:
Coffee Stain Studios is known for developing the original Goat Simulator and its several expansions aside from GoatZ, such as Goat Simulator MMO Simulator and Goat Simulator: Waste of Space. They are also the developer behind the Sanctum series, a unique blend of tower defense and first-person shooter, and Deep Rock Galactic, a co-op first-person shooter featuring space dwarves and mining expeditions.