Zebras occupy eastern part of the Old World because of savannah on the Cutiemap at the west from Equestria and, well "Fallout: Equestria" where they are used as China. They are rather unstable feudal empire where small tribes live by the old ways under protection of mighty kings who have actual armies.
Raiders are recruited from the tribes as part of payment for protection. Like tribal chargers they use their wearpon with mouth thus being able to run properly while attacking and becoming useless in close combat against a shield wall. To compensate it they carry a few javelins.