Just tested, the greatbow does ~80 damage using cheap wooden arrows, a Glock 9mm does ~40-50 with common 9mm JHP against a regular zombie, or almost double the damage.
Against a hulk, the situation is even more dire, with the greatbow still doing ~76-80, while the 9mm gun is doing ~25-30 damage. The faster rate of fire helps a little, but neither is able to drop the hulk before it can cover the 12 tile testing distance and take a swing at the player, at least not using basic ammo.
Using carbon fiber arrows, the greatbow jumps to ~100 damage against a regular zombie, and same against a hulk, dropping it in ~10 tiles. The +P+ ammo deals roughly 50-60 damage to the regular Z, and ~40-50 to the hulk, and a 15-round magazine just barely dropped it before needing a reload.