This ZIP to RAR conversion does not run here
RAR is familiar, but it is not a format a website can write.
RAR creation is not available here.
What to do instead
Send the ZIP. Recipients on Windows, Mac, and phones can open it without extra software. Use RAR to ZIP if you are trying to unpack a RAR.
The page that does work is RAR to ZIP.
Why ZIP to RAR is its own job
ZIP to RAR sits on this site because ZIP and RAR are not interchangeable, even when they look similar in a file list. RAR is familiar, but it is not a format a website can write. ZIP is the file you send when you do not know what the other computer has installed. People convert RAR to ZIP so Windows and phones can open the download without an extra app.
RAR creation is not available here.
The ZIP file you already have
ZIP is the archive everyone can open. Windows, macOS, and phones all understand it. A ZIP of a PDF is not a meaningful compression of that PDF. Password-protected archives fail.
Keep the original archive until the ZIP has been opened on the other computer.
What a RAR result is for
The download has to be RAR, because that is the format the next step named. People convert RAR to ZIP so Windows and phones can open the download without an extra app. Many RAR files can be unpacked locally into ZIP.
Password-protected RAR will not open. Test the ZIP before you throw the RAR away.
How to tell that ZIP to RAR worked
ZIP to RAR is worth using only when RAR is what the next step actually named. RAR is familiar, but it is not a format a website can write. What you get from ZIP to RAR: RAR creation is not available here. Before you trust it: Send the ZIP. Recipients on Windows, Mac, and phones can open it without extra software. Use RAR to ZIP if you are trying to unpack a RAR. The file stays in your browser and is not uploaded. The limit is 100 MB. Keep the original until the download has been opened in the program that will use it. A second pass rarely helps. If the first RAR file is rejected, read the error from the program that rejected it. Another conversion of a bad result usually makes the file worse, not more compatible. When you are done, you should still have the ZIP original and one RAR download that you have opened. If those two are the same kind of failure, this was the wrong tool and the page above is the place that says so. Open the archive ZIP to RAR gives you before you delete the one you started with. Password-protected files fail. Some Unix downloads hide a TAR inside gzip or bzip2, so one conversion may not be the last step. ZIP is the file you can hand to a phone or a Windows PC without an extra app. Creating RAR or 7Z still needs a desktop program.
Here is the decision for ZIP to RAR. You start with ZIP and you stop when a real program accepts RAR. RAR, 7Z, TAR, gzip, and bzip2 can be unpacked into ZIP here. This site cannot create a new RAR. Split and some solid archives fail. If those two sentences describe a tradeoff you do not want, do not convert. Renaming the extension by hand will not do this job. Running the tool twice on its own output will not do it either.
Send the ZIP. Recipients on Windows, Mac, and phones can open it without extra software. Use RAR to ZIP if you are trying to unpack a RAR.
A related step, if you still need one, is 7Z to ZIP.
Other jobs start from the homepage, where each tool is named for the conversion it actually does.