Well never having used 7za (the command line tool) it took a few minutes
Code:
for /r %1 in (*.original_epub) do 7za a "%~p1""%~n1".7z "%1"
This will create a new 7Z archive within the same folder that the original_epub file was located with the same name as the original_epub that contains a single file.
There are NO processes left running after this command; the only issue is that I'm not sure how to have 7za drop the file after it has been added. This could be done by a second for command
Code:
for /r %1 in (*.original_epub) do del "%1"
PS: I only SAW your reply about 10 minutes ago; in that time I located the 7zip command line version, installed it, wrote the batch line, tested it, AND wrote this message.
PPS: Quite likely no need to compress due to the fact that an epub actually IS a zip file (albeit with the possibility that not all components of it might be compressed. So one could add the -x0 switch to the command line