CircularFLO is intended to be easy to use for all InDesign users including those who prefer clicks to code.
However for those curious enough to look into the code, who wish to add more or we recommend ePub Zip-Unzip 64 3.0 available free from here which we use in order to be sure we open up and repack the EPUB correctly.
Once downloaded, drag an EPUB onto the tool to unzip it properly. Drag a folder onto the same tool to rezip it up to an EPUB.
If you have amended the code it is recommended to validate the EPUB again.