This error often appears when the zip includes the containing folder, rather than having the files in its root. If that doesn’t solve the error, I suggest you post the file somewhere so we can give it a look.
Did you change the extension back to .zip? Once I change the extension to .zip, I am able to uncompress with no problems. And I just created it by right-clicking on the folder on my Mac, which just uses basic zip.
Thank you! Yes, you’re right – instead of zipping the entire directory, I had to go inside the directory and select all the contents that I wanted to zip. And then I ran zip -d filename.zip __MACOSX/\* to remove the hidden files.