There are a lot of methods to do this, and it can seem tricky as the
Hunk of Meat weapon does little damage and gets "stuck" in an enemy for a while.
The trick is to have 2 hunks of meat in your inventory and to weaken a zombie before hitting them. Go to the Medieval Town inside of the mall. Use the ledges to scale the castle and go inside to find two permanent Hunk of Meat spawns; pick them up. Now lure a zombie away from a crowd and damage it using a weapon like an assault rifle or sword. Now use both your hunks of meat to repeatedly hit the zombie until it dies. When you have two hunks of meat, you can "juggle" them while hitting him. You can also freeze the zombie and then hit them to kill them,