Yes, I understand that you have a package ZIP file containing an XSLX. You upload the ZIP file, not the XSLX file and you see that the ZIP file was uploaded, therefore it seems to work correctly.
Of course that you can give the ZIP file any extension, e.g. .jpg, but the name doesn't change the content. It's still a ZIP archive, just with a misleading name. Using a wrong extension gives you no benefit, just confusion and less comfort (e.g. because the default program for opening a file is picked by the extension), therefore you shouldn't do that.
Before we go into discussion how to create a package, please confirm that your intention is using a package import and not just importing an Excel file. It's possible that you're confused by the options and/or those two distinct data management APIs. You didn't tell us whether you can import the file manually, but I believe you can't. If you want to import an Excel file directly, you shouldn't use a package (ZIP) and if you want to use a package, you didn't seem to create it in the right way.
I don't want to go to details of all the possible options. I'll wait for more information about your intention.
