Answer by JdeBP for Convert file path from Linux to Windows format for Wine tool

Your script is actually very close. All that you need is the winepath tool, that comes as part of WINE, to do the conversion:

#!/bin/sh
exec wine /utils/wincmp.exe "`winepath --windows \"$1\"`" "`winepath --windows \"$2\"`"

Or using Laurent Bercot's execline:

#!/command/execlineb -S2
backtick -i left { winepath --windows $1 }
backtick -i right { winepath --windows $2 }
multisubstitute {
    importas left left
    importas right right
}
wine 
/utils/wincmp.exe ${left} ${right}