I think the problem began after the latest NVidia update (not very sure!)
Although i have set the monitor mode not to fade into dark in my energy saving settings of zorin the hardware switches to black after several seconds.
I found some hints in the internet that "ubuntu" does the same thing in certain circumstances and hardware environments.
So i investigated that i had to check if DPMS is enabled or disabled.
-> commandline
xset -q
delivers that it was enabled
-> commandline
xset -dpms
disabled it and made a bash script in my homedir and made it executable and set it to start automatically after re-boot.
For now the monitor behaves like before the updates and doesn't fade to black any longer.
Anyone else the same?