Depend on what kind of zombies we are talking about, the location and my current items on hand at the time.
Worst case scenario, a few hours, best case, a year, two years tops.
I am going to say Doomsday. It's a DSMP Song about the UTTER DESTRUCTION OF L'MANBERG (v.2), but it has the message that "betrayal is wrong" behind it. Well, that's what I see.
Another is Celestial. Ed Sheeran. People who haven't seen the music video may think he's talking about a girl (again)...