You'll note that all functions begin with the letters Unzip. To avoid conflicts with RxUnzip function names, do not name any of the functions in your REXX script starting with those 5 letters (neither upper nor lower case). Also, do not use the variables ZipErr and ZipHeading for purposes other than setting error handling features.
The sections of this book leading up to the list of functions describe how to do various tasks with the RxUnzip functions. So, they are overviews (ie, tutorials) of how to use RxUnzip in various ways, whereas the list of functions are more of a reference complete with incidental notes/details.