Invincible robot zombies are a deliberate reference to The Walking Dead
Invincible and The Walking Dead may not have much in common, but thanks to Robert Kirkman, the former has a villain that references zombie comics.

Superhero series Invincible appears to have deliberately withheld references to hit horror film The Walking Dead. Series author and co-creator of both comics, Robert Kirkman, refers to a specific set of villains in his Zombie book.
"Invincible" focuses on the life of Mark Grayson, the son of the world's most powerful superhero, Almighty. After years of wondering when his powers would come into play, Mark finally developed the same abilities as his father, making the young man invincible. However, Mark discovers that the Almighty is actually a member of the invading alien race, the Viltrumites, leading Mark on a bloody road to discover his true destiny as a hero. The critically acclaimed manga, which was eventually adapted into an animated series on Amazon Prime, is also a hit.
While Invincible was a popular title at Image Comics, it wasn't the only work in the publisher's library that Robert Kirkman worked on. After all, Kirkman is also the co-creator of the hugely popular series The Walking Dead. Although the two series focus on very different themes, Kirkman occasionally touches on another. In Invincible, Mark Grayson encounters a villain known as The Walking Dead, a name that apparently refers to Image's zombie series co-created by Kirkman. The Walking Dead is a gigantic resurrected corpse that behaves no differently than the walking dead in The Walking Dead. This isn't the only time other Kirkman properties are referenced by Invincible. The variant cover for Invincible #20 shows Mark fighting the Reanimen, titled "Walking Fear: Return of the Robot Zombies". Not only that, but the cover is shown in black and white, much like The Walking Dead's color scheme.
Why Reference The Walking Dead In Invincible?

Superheroes are common in Invincible. The entire story is a nod to the superhero genre, so it's only natural to see parodies of the Justice League or various other comic book superheroes or villains. References to other genres, especially zombies, are rarely seen in the series. But The Walking Dead does come from the creator of Invincible, so sneaking a reference to at least one of his other hit shows isn't the boldest idea for Kirkman.
Invincible and The Walking Dead may be two completely different series, but they share a common theme of maturity And there are a lot of bloody scenes. The Walking Dead is undoubtedly one of Kirkman's most popular series, if not Image's most successful comic. He probably knows readers will be excited to see his other ongoing series refer to growing cultural juggernauts. Invincible and The Walking Dead might not be the most obvious of siblings, but they have an interesting connection thanks to a shared co-creator.