This works for me:
Create myscript.bat and put into it (note the single quotes around the commands to be executed in superuser mode):
adb shell "su -c 'command1; command2; command3'"
then run myscript.bat from a DOS shell.
Note: it doesn’t appear that the the DOS line continuation character (^) works in this situation. In other words, the following doesn’t work for me:
adb shell "su -c '^
command1; ^
command2; ^
command3'"
This results in “Syntax error: Unterminated quoted string”