I have no clue but I'm just gonna throw this idea out there.
What if you install into a folder both installations can share.
ie if you had another non OS partition/HD both saw such as
e:/zimbrainstallfolder
I don't know what all is installed in that folder vs other system folders (and what might be OS specific) but it might not hurt to try it.
Maybe install to the same directory in both OS's that way if there are system files installed to %WinDir%\system32 both will have the necessary files.
WHAT I'M SAYING IS PROBABLY CRAZY AND MIGHT GIVE YOU PROBLEMS SO BACKUP YOUR STUFF AND TEST IT FIRST. 