Record labels have already done the work for you. Look for box sets like "NOW That’s What I Call Music – 100 Hits" or "Time Life: The Greatest Hits of All Time." If you buy the CD or digital album, you are legally allowed to rip those songs to your computer and compress them into your own personal ZIP file.
One of the biggest challenges in finding this download is realizing that there isn't just one list. When you search for a zip file, you are likely downloading a specific entity's opinion on the best music. Here are the most common compilations you will find: Top 100 Songs Of All Time Download - Zip