Hi @Odelle ...
Thanks for the additional information. This is interesting. I just tried exporting two different courses that I have access to, and both of them produced *.imscc files (not *.zip) files. One *.imscc file was almost 200 MB in file size, the other was only about 17 MB in file size.
Also, when I look at How do I export a Canvas course?, the second paragraph in the light blue box at the top of the page says, "Exports are packaged as IMSCC ZIP files, which can only be opened by programs that support Common Cartridge files. You can also change the extension from .imscc to .zip and treat it as any other ZIP file." From my own interpretation, that last sentence implies that the file produced from the export is *.imscc, but that instructors and admins can change the file extension to *.zip (not the other way around).
Have you or your colleague tried exporting other courses using this same process? Are they also creating *.zip files? Or, are *.imscc files being generated for these other courses?
Ultimately, this might be a question you need to contact Canvas Support about so that they can look into the issue for you in more detail. If you do choose this route, please come back to this thread to provide an update so that we can learn more and know if were able to find a solution.
Thanks. Looking forward to hearing back from you soon.