Yeah, it’s mainly licensed work (there’s also Dead Island) and the occasional shambler showing up in other series (like Criminal Macabre, The Goon, etc). Mignola is only part of the Zombieworld series of limited editions but they know what sells, so his is sold separately. It’s a lesser work and he isn’t on art duties but if you are jonesing for more from him then this the next stop. I’ve also read the others (in the Winter’s Dregs collection) and they are fine but there are likely better zombie comics out there - I largely read it for the Pat Mills and John Hicklenton as the latter died too early and his art is out there but there is so little of it you have to hunt down what there is (the story is suitably over-the-top, so I wasn’t disappointed).