If you did not download this file yourself from an official store, be cautious. Zip files labeled with product codes are sometimes used to distribute malware or unwanted software on file-sharing sites. It is recommended to:
Most likely DLsite , a major digital storefront for independent (doujin) creators.
This would help in providing a specific review of the content itself.
Use a security tool like VirusTotal to check the .zip before extracting it.
.zip files on these platforms generally contain the game assets, audio tracks (WAV/MP3), or image folders. Warning on Source Security
RJ codes are typically used for voice dramas (ASMR), independent games, or doujinshi.