Zombies and mathematics looks like it would be two things that didn't quite go together. Andrew Miller had a project-based learning project about Zombie-based Learning.
With math and zombies most of the material has to do with diseases that increase at an exponential rate. Students could analyze different population centers and predict its spread using exponential functions. They could determine when everyone is infected and map the spread using the math data they calculate, or even explore the rate of decay. Students could also investigate what happens when a certain number of people are vaccinated to help prevent the spread.
These are some ideas that have been implemented as part of a PBL project or would be a good entry point for zombie-based learning across the curriculum.