What are .zip files and how do I open them?
We’ve created a .zip file to store all of the eBooks in one downloadable package, because it compresses files and there are just SO many files included in this bundle. This helps to make it a lot easier and faster to transfer and download the eBooks.
Here are tutorials for opening .zip files on different computers (Windows, Mac): https://www.hellotech.com/guide/for/how-to-open-a-zip-file-windows-mac-iphone-android
As long as your computer is relatively new, you should be able to open the files up without the help of any extra software.
Zip files are not recommended to download directly to any mobile device.