Compressed library vs. Zipped

I have been trying to compress my library to email to my lecturer. Whenever I try to Compress Library with attachments, I get an error message: “EndNote cannot save or create this file. Make sure the disk you want to save the file on is not full, write-protected, or damaged.” I have attached the error message.

The lecturer said not to bother compressing the library, but instead zip the library and .Data files. I thought that is what happens when one compresses the library.

How does one .zip the library and the .Data files? Am I missing something?

EndNote error for Compressed library.jpg