How to upload zipped projects to

I have a base application I would like to share, but doesn’t accept zip files on upload.
I have noticed however that others have successfully uploaded such projects.
I can of course change the extension to ots, and the file will be uploaded, but after I submit it for publication, it will not be accepted, I get a notification later that the status of my project changed to private.
Maybe the application is not appropriate for the website’s purposes (it is a recipe organizer program), but I wonder how others could upload similar projects.