a zonebox is found in data folder
why not try another thing, and that is changing the mesh of an already existing door? i dont know if it's possible, but you can try modding dying light.
so if you unpack the files from the game
you get access to the game files, and in there, there is a file called presets/doordi.pre
move that file into your data folder project (into the folder presets)
that file has the visual meshes for each door.
so, import a custom door model into dying light (my_door.fbx -> import into default folder).it creates a .msh called my_door.msh.
now write my_door.msh where it says lab_door_a.msh
and reload the tools
then select the doorDi object on the map, select that preset with your custom door, and set the materials for your custom door. (like for the reflection example)