Okay, made a fresh backup copy from the original folder, and also used the "C&C Ultimate Collection Launchers Setup" used by the OP of this thread:
https://forums.cncnet.org/index.php?topic=6744.0
It's got the generals_origin.exe error message, and any error messages that existed before involving duplicate files are gone - part of the launcher works, since the resolution change to 1920x1080 works, but it's still only playing ZH.