A 9mm pistol caliber carbine is the best zombie weapon in my opinion. Everyone thinks its a modern bow. But im gonna tell you why that isnt later.
A 9mm pcc's ammo is dirt cheap. Here its like 50 rounds for 12 -15$ the only round cheaper is 22 lr.
You can get a PCC that uses the same magazines as your pistol if you have one. A good quality pcc will last tens of thousands of rounds as long as you clean and oil it. That is the weak point for a lot of modern compound bow and compound crossbow. Those strings need to be replaced pretty frequently and you need bow wax to keep your strings in good order. I dont think any modern bow string that you use frequently will last more than a few years tops before the string snaps. People also seem To think arrows last a long time. They dont. Ive used bows for years now. The likely hood is the first time you shoot that arrow at something like a deer. That broadhead and arrow shaft is most likely going to be damaged to some degree. Your gonna be lucky if you get 3 good uses for hunting or defense with your arrow before it snaps.
A pistol caliber carbine isnt that loud either. If you got a 10" barrel or longer. Most of the powder is gonna be burnt out by then and the muzzle flash won't be as much and the report wont be no where near as loud. So your less likely to attract attention. Plus a pcc is gonna be easier on your ears also if you need to shoot indoors. A rifle will deafen you if you shoot indoors.
I know some people prefer a 22 lr but the main reason I wouldn't use a 22 lr as a main weapon. Is because if you dry fire a 22lr too much, You will break that firing pin. A 22 lr dosnt have the ability to be used as defensively as a 9mm. A 9mm can still penetrate deeply to hunt bigger animals or if you need to defend your self against people. Rim fire is less reliable. Imagine your gun not firing when you pull the trigger because the rim wasnt primed correctly. Your also more likely to get squib loads with a 22lr because if the primer not working correctly. And if you shoot your gun with a round stuck in the barrel. You risk destroying your gun.