I recommend the novel "Global Overlord: I've Become a Zombie." Similar to the novel in the given information, the protagonist became a zombie at the beginning of the apocalypse. His body did not rot, but he could not speak. Through evolution, the main character gained the ability to eat souls to reduce damage and speak. In this novel, the protagonist also evolved by eating xenogeneic creatures, but he used the evolution system, unlike the characters in "Love You, Doom Doom" who evolved by chance. I hope you like this fairy's recommendation. Muah ~😗