Issue:
The whole background of design center is black and there is nothing you can see except the icon, as below shown:
Causes:
Somehow the background color of design center isn't configured right in Style.zus files.
Solution:
Delete the Style.zus file to try, if problem not solved, then delete the whole "en-us" folder and then try to restart ZWCAD again. The folder is located in this path:
C:\Users\[username]\AppData\Roaming\ZWSOFT\ZWCAD\2018\en-US\Support