OK, first off, which .iso of Zorin 17 did you download. The Dell Latitude 7400 is certified hardware by Ubuntu:
https://ubuntu.com/certified/201902-26863/18.04%20LTS
This would equate to Zorin 15! Zorin 15 became E.O.L. in April 2023.
In respect of the RST question, in order to get Linux to install you will need to turn RST off in the BIOS and choose AHCI instead. You will also need to turn bitlocker off. Once RST is turned off you will not be able to boot into Windows. Other actions you need to take include turning off fast-boot in the BIOS, and before you make all the changes in the BIOS, boot into Windows and show hidden Power Settings and ensure the Hard Drive is set to have it's sleep function turned off. From Windows 8 and up, Microsoft designed the system to keep the hard drive in sleep mode (it never gets fully turned off when you power down) to enable quicker boot times.
The version of Zorin 17 you are using is critical, as early versions default to a Wayland compositor instead of xorg. From another recent posting a member submitted a screenshot that indicated Zorin on xorg was the default compositor, so ensure that you download Zorin 17 r2 and verify its checksum before burning to DVD/USB.
You also might want to give Linux Mint a try, or Q4OS KDE and see if things such as brightness functions work with those.
I have included instructions on how to check the SHA checksum of an .iso in the Unofficial Manuals I wrote for Zorin 15 and 17.