1.) Click "file" then "export library" in the top left of your Zotero application as indicated below.
2.) Choose to save the file as an Endnote XML (.xml) file type under the "format' dropdown menu. You can export both files & notes, both of which will import successfully to ReadCube. When finished, press the "OK" button.
3.) Name the file "ReadCube Library" and save it somewhere easily accessed, such as your desktop.
4.) Drag this file into the import screen using ReadCube Desktop.