Killing Invisible Zombies Guide
Listen for their sound, you can locate them by their growling.
Stick your hand(s) in front of you at eye level and grope for their head, and grab it.
Once you have their head you can kill them with any gun. The easiest way is to use a shotgun or any gun that doesn’t care that it’s armored.
You can also lean their head way back and shoot upwards towards their chin, or lean them forwards and aim at the back of their head. It’ll take a few bullets, but if you’re lucky you’ll one-shot it.
Explosives and such do the job just fine as well. Just get a basic idea of where they are and let rip. Getting on top of a car or some other high ground will let you gather them and their friends and get a multi-kill.
If you’re stamina gets low, let them go and back up until it recovers. Try to eliminate any other zombies nearby before you deal with them, even if you have to hold them with one hand and kill their friends with the other.