This achievement is pretty easy.
Simply load the GoatZ after outbreak mode.
Use the wall run to get on the roof of one of the houses in the start area where u should be safe.
Now activate the mutator that u don't have to eat so that u can't starve.
Simply wait now for round about 30 min. (3 min per day)
and the achievement should Pop.
if u have any improvments please comment :)