I found a fix to my problem. I contacted the Asus support service and they said it has to be a GPU problem because the cursor can be seen. So I went to Control Panel -> Hardware and Sound -> Device...

I have very similar problem as the OP. An external monitor connected to the docking station shows only black screen and the cursor. The setup is following:
- Asus ZenBook UX303LN laptop
- Asus 24"...