If you're looking to download the album zip file, you can find it on various music streaming platforms or online stores such as:
The band actually recorded an entirely different album called Cigarettes and Valentines before American Idiot , but the master tapes were stolen, leading them to start from scratch. Green Day American Idiot Album Download Zip
These high-fidelity stores sell the album in CD-quality lossless formats (FLAC/WAV). If you want the zip file for archiving, this is the gold standard. If you're looking to download the album zip
You can buy the album digitally for roughly $9.99. You download the files as DRM-free (Digital Rights Management free) AAC files. You can convert these to MP3 or zip them yourself for backup. but the master tapes were stolen