Below freezing, zombies slow down. In hard frost they freeze solid and cannot move until they thaw. That makes winter the season for clearing cities. Salvage teams go into dead cities in winter and pull out before the spring thaw.
Hot dry air dries zombies out. Over the years they become brittle Husk Zombies. Deserts hold few zombies, so desert roads are some of the safest land routes. The Husks that are there are silent, so watch your back.
Zombies cannot swim. A zombie that goes into deep water sinks and walks along the bottom. Cleared islands stay clear, and ships are the safest travel on Earth. Be careful at riverbanks and beaches. A zombie that walked into a river can walk out on the other side.
Zombies have poor eyesight, and it is worst at night. Their hearing and smell still work in the dark. Moving at night is safer only if you are quiet.
Zombies hunt by smell after sound. Wind carries your smell. Staying downwind of a group of zombies makes you harder to find.
The big hordes drift with the seasons along old highways and rivers. They move more in warm months and slow down in the cold. The summer horde migration across the Great Plains is the biggest every year.
The Z-Virus slows rot, so zombies do not fall apart quickly. Old zombies dry out into Husks. New zombies rise every year from people who die infected.