Better than average modern zpoc though tbh a fairy basic read.
Okay, my gripe. The author claims this is intended for 25-40? This is a serious disconnect with the adult mind. These books are Young Adult. Naughty words and a little gore don't make a horror nor do they mean they're adult books? It's something I come across often with modern authors.
To create a zpoc book aimed at adults you need a dark atmosphere, especially when it's horror. This series is too much action, little in the way of tension building, chilling, oppressive scenarios that induce fear.
Omega Days book 1 by John L. Campbell, the author should read for everyday gritty reality. Dark horror, read Apocalypse Crusade book 1 by Peter Meredith. Chilling atmosphere, try reading Alaskan Undead by Sean Schubert. Bleakness, Winkless should read The Last Plague by Rich Hawkins (especially book 2). Adult conversations and sociopolitical context, try The Living Dead by George A. Romero & Daniel Kraus.
Then come back with a new series Lance.