Here's a video of a mission I set up for my group using this mod. The players had no idea they were going to confront zombies until the reveal at 37:20. I only used the slow zombies as I plan on surprising the players again in the future and I want to save some of the other available zombies for those sessions.

https://www.youtube.com/watch?v=5CrhHduLnHA&t=3732s