As shown in the video put your back against the railing then get the zombie to slap you while jumping backwards and you should land on the railing. Then get him to hit you again while jumping and you should be able to get on top of the computers. If you find the second jump difficult you could also dolphin dive onto the computers. Have fun
+Rep/Thank if my glitch was useful.
The following 10 users say thank you to J-Andrade for this useful post: