This is connected to "I am a Hero" in-name only. The stories are not set in the same fictional universe, and the work is more centred around the idea of zombies thematically, and uses the "I am a Hero" brand to draw in people who would otherwise pass over it. This is not necessarily a bad thing, but I think fans of IAAH should go in with their expectations appropriately tempered
It is in general a pretty mediocre group of stories. Several of them dont even include zombies. Chapter 1 for instance is basically just softcore porn, with only the barest hint of connection to a
zombie storyline. Another story is basically a slice of life romance, with some zombies in the background to keep things interesting. So considering IAAH is regarded as probably the best Zombie manga ever written, and these stories arnt especially good or even particulary related to zombies, you can see why this work is a bit of a let-down. Of the 8 chapters, "I am not a Hero" and "she is a slow walker" are pretty good, the other 6 are pretty much totally forgettable.
To expand on that caveat: the Junji Ito story is well done. It has good art, an entertaining premise, and is the closest to an actual story about zombies from the whole anthology. If you are a fan of Ito, this is another solid work from him, and almost makes up for the generally low quality of the rest of the stories. "I am not a hero" isnt amazing or anything, but its got the same weirdly comedic horror vibe of the original series, and stands well on its own.
TLDR: The Junji Ito story is good, "I am not a hero" is ok, everything else is entirely mediocre, 5/10.