A more logical way is to go to "mounts and storage" / "mount /storage/sdcard0" rather than misusing "flash zip from sdcard" for mounting the card.
I guess there is a symlink /sdcard pointing to /storage/sdcard0; if not, you'll have to edit the script before running to get the path right.
I guess there is a symlink /sdcard pointing to /storage/sdcard0; if not, you'll have to edit the script before running to get the path right.