Please try this rom: Z97XU7TH_HighSierra.F6.zip I replaced CSMVideo with HermitCrabs patched one this should help to overcome the black screen Error.
Thanks for the help! However, that didn't help
I still have the black screen identical with the previous patch.
However today, while experimenting with the booting disc order in the BIOS, I could make the computer boots for a moment but the « no boot disc » icon appeared when the booting bar was half done. The Motherboard was indicating the error 51 (Memory initialization error occurs) during the boot, so maybe I have an issue with my RAM. I tried booting with one stick only then the other with no success : direct black screen. Also by default, my ram is at 1333 Mhz while it should be at 1600 Mhz. To get these 1600 Mhz I have to choose Profile1 in the BIOS. That doesn't affect my booting issue, unfortunately 
Also, I couldn't repeat the half boot.
For the record, I tried with older BIOS patch that wasn't made for High Sierra, just to compare. I never have a black screen with but I only half boot. That wasn't a surprise, of course 
@al6042 :
Danke für die Hilfe, aber ich versuche nur von dem USB Stick Installer zu booten, den ich aus dem macOS Installer gemacht habe. Ein Vanille-USB-Stick. Ich habe keine EFI-Partition darauf. Ich konnte macOS nicht auf einer Festplatte installieren.
- /dev/disk3 (external, physical):
- #: TYPE NAME SIZE IDENTIFIER
- 0: FDisk_partition_scheme *32.1 GB disk3
- 1: Apple_HFS Install macOS High S... 32.1 GB disk3s1