I recommend you to not store the library files in .zip format in the repository. By doing that you have lost much of the benefits of Git version control and it makes it more difficult for anyone to collaborate on your project. There is really no reason to put the files in a .zip because GitHub automatically produces .zip files of the repository. You can download the contents of the repository at any point in history via GitHub's Clone or download > Download ZIP button. A zip file link will also be automatically added to any release you create.
Regarding the whole int/long thing, it seems like it should be possible to make a single library work for either. If not, then you can create a separate repository for each version of the library or separate branches if you prefer to keep them in the same repo.