Outnumbered Volume 4, The Zombie Apocalypse Series

At the beginning of the Zombie Apocalypse, there were approximately three-hundred-thirty-five million people in the United States of America. My gut feeling is there are far less than fifty thousand humans alive now. Even that equates to only one thousand people in each of the fifty areas previously known as states.
A year after their inception, zombies outnumbered humans by about 7,000 to one. Each man woman and child must terminate that number of zombies before the undead horror ends. Now, say we do eliminate the undead menace in the next decade, what then? The national electric grid is down and deteriorating; it can never be recharged. No power plants or oil refineries remain operational to supply energy. All modern manufacturing throughout the world has ceased completely. Fuel to run generators, vehicles, and furnaces will be depleted or contaminated in the next decade. Horses will replace fossil-fueled vehicles. Robotics and assembly lines will be replaced by manual labor on a miniscule scale. Of necessity, homes will be smaller and will be made of stones, logs or mud.
Mankind will revert to conditions of the fifteenth century; we are not emotionally or materially prepared for that upheaval. Everything humans need to survive will be handmade by people in centralized communal settings. We prepare for the new old world because we are on a downhill run to the past.