Sounds a bit brutal, but all in the name of fun ha ha!! I have done airsoft and paintball, and I am assuming they are tame compared to this.
So what are the events like in terms of kit you wear, type of games, and how do you 'kill' the zombies etc??
When you need to sign a disclaimer to say you've signed the disclaimer and one of the first things you get told is "Don't take the pee because these guys won't take your crap" you know it's going to be a good day!
The one I done you got kitted up in riot helmets, knee and elbow protectors and a chest rig all which instantly make you boiling hot before you've even moved!
Then we had a couple of training sessions, one with riot shields and training batons and another with the paintball M16s and room clearance.
Then you get given your shield and baton loaded into the back of a transit van driven round a bit and kicked out at an abandoned warehouse and all hell breaks loose you've got about 10 "zombies" flying at you from all directions, throwing you all over the place and you've basically got to batter them with the training batons.
They die when they feel like it so you can be hitting and throwing and getting thrown around a lot before they go down and they normally get back up when your back is turned.
After that we had a break for lunch then got loaded up with the paintball kit back in the van and back to the inside of the abandoned warehouse this time where you got ambushed for every angle and basically just had to shoot and hope while getting thrown around again.
Hard work but great fun, all the guys that ran the one I went to were ex or serving forces and seriously fit but up for a good laugh.