The MP3 recordings  you download from mypurchase.assimil.online  have been compressed in ZIP format.
Depending on your device, once the download has finished you may be required to decompress the file before being able to use it. It is generally preferable to decompress the file. This will enable you to more easily browse the directories and to read the files more quickly.
These files are frequently large and may exceed 1 GB.
When you open your ZIP file (decompression), if your computer informs you that the file has been corrupted or is invalid, we suggest you download it again. There was probably an error the first time. You can also try using a different browser.
(For using on an iOS device (iPad or iPhone), on your computer you must first of all (Windows or macOS) add the MP3 files to your iTunes/Apple Music library and then synchronise them with your device.)