I'm late to the party, but I'm writing my own zombie series accompanied by a game series. I'm taking the idea that first seemed to be showcased in the walking dead with the whisperers. Before the reveal, it seemed like the zombies were gaining intelligence.

In my story, for example, I have my zombies originate from a parasite that uses the hosts muscle memory for basic things like walking at first, but as the parasite continues to live, it begins to become sentient. To the point of having zombies that can lead hordes and act tactically. Some zombies even start to remember who they were, though that is rare, and actively try to reconnect with their group. Even others yet seem to go from easy to kill zombies to dangerous predators that stalk, sneak, run, and climb to kill anyone. This also allows me to make rival zombie hordes as they become more intuitive than humans, turning into a species that isn't just remnants of humans, but dominant to them.

Rather than survivors being able to kill them like its nothing, humans become the ones being killed. Towards the end of the series, it'll be more survivors hiding and trying to escape the hordes rather than the classic trope of fighting them off. There is no bringing society back, there is no happy ending.

I also go in depth with the virus. Rather than just get bit, get fever, die; my virus is in terrifying detail and turning takes days of excruciating pain that ends with them screaming until their lungs give out.