_Michael_
Troubadour
It would go something like: ‘we have an historian in the group’ who would be the underdog, and then they would be able to direct the others on how to recreate any number of unfathomable historical tactics, and it would make for a great fictional part of the plot.
But you also have to consider that doing anything like that would take planning and provisions, which in a zombie post apocalyptic shitstorm would be far easier said than done. Especially if the zombies can run.
They need motivation to make those curtain walls and find those provisions. I just happen to know someone who is the perfect labor organizer.
EDIT: Would explain why most of the castle builders of the medieval era were all warlords...