I've said other places that if I were in some sort of situation like this, my preferred close in weapon would be a Japanese Katana or Naginata. Relatively silent, effective, and an arms reach kind of weapon.
Firearm choice?
Easy. A .22. Something like a Ruger 10/22 with a bunch of high-cap magazines. Relatively quiet, which is a huge benefit, when the zombies are drawn by sound, not much kick so very fast recovery time, fairly easy to suppress by do it yourself means, and will do more than enough damage to the brain to stop a zombie.
This.
Suppressed (or not) 22LR with a decent scope, plus as much ammo as you can carry.
Go to a reasonably tall structure (say 30-50ft)
Destroy the access to it (bring a rope)
Start shooting zombies.
Lets say you can carry 40 bricks of 22LR, and you average one to two shots per zombie,
And zombies can hear an unsuppressed 22 out to a mile or so.
That's 10,000-20,000 zombie kills, or fully depopulating an area with a population density of 6-12,000/sq mile...or a VERY dense city.
(note, assuming they on average get 50yds away, that's a pile of zombies 50yds in radius and only 1-2 zombies deep.
Pour some fuel oil on the zombie pile, light, and leave
Then, move to a new location and resupply.
That's 150lbs of ammo (and about $1000-1200 bucks)
In terms of rate, let's say zombies travel at a slow shamble (about 0.5-1 mile per hour), you will have to shoot quasi-rapid fire (a shot every 1-2 seconds) to prevent a zombie-pile from reaching your 30-50ft altitude.
But still, this shows that with careful planning, zombie depopulation even in dense cities is totally reasonable
