The zombie must remove the board on which you are, but, in a special way, the board must go up when the zombie removes it.
Good LAG timing is needed (I've done it with Wireless LAG).
Enjoy!
Please watch the entire video before saying it's old/been posted etc!
So find me a video of someone doing the same thing as me from 1:30 until the end.
So basically you get outside of the map by doing the glitch to get through the window but with the other board on there and hope it pushes you up instead of out?