1- Go to your steam folder
2- Go to DayZ/Addons folder
3- Locate ANY *.PBO file you want (for example "assets_buildings2") and DELETE it
4- Find any other (preferably smaller) *.PBO file, copy+paste it into the DayZ/Addons folder & re-name it as the deleted PBO
5- Reproduce as many times as you want to eliminate trees, houses, structures, etc.
6- You can now see, run and shoot trough walls and buildings.
7- Annoy and ruin everyone's fun & will to play this game.