The Croppic library (http://www.croppic.net/) does not provide for zooming images below the container size. However, this can be solved by modifying the zoom() function in the library file: https://github.com/sconsult/croppic/issues/100
I have tried doing this in various ways, using the information in this issue, but nothing works. I'm doing something wrong and I don't know what.
Example: https://github.com/rudolphreti/croppic_example/
Example from github online: https://srv19859.microhost.com.pl/croppic_example/