The Omega Dog (Pavlov's Dogs Book 2)
by D.L. Snell
Twisting and turning through hordes of zombies, cartel territory, Mayan ruins, and the things that now inhabit them, a group of survivors must travel to save one man's family from a third world gone to hell. But this time, even best friends have deadly secrets, and even allies can't be trusted - as a father's only hope of getting his kids out alive is the very thing that's hunting him down.