If you prefer managing local files on your computer or high-res audio player, you can build a clean, perfectly tagged library by purchasing digital tracks individually or by downloading playlists via official offline subscription features.
While not a "zip file" in the traditional sense, apps like Gaana, JioSaavn, and Spotify (Premium) allow for high-quality, legal offline downloads of entire playlists.
Start with the Google search operator: intitle:"Ilaiyaraaja" intitle:"ZIP" "320kbps" -torrent -spotify and click the first result that is not a blogspot ad. Happy listening!
YouTube hosts extensive, user-curated playlists and official audio topic channels dedicated to Ilayaraja. Users with a premium subscription can download these massive compilation videos and playlists directly to their devices for offline playback. Spotify and Apple Music