File Conversion – Is it possible to convert .rar to .zip in Google Drive?

No, it is not possible at all without downloading it first. File extensions may be renamed, however, it will still be a file. RAR.rar file called ZIP.zip (and if you download it, it will be Zip.zip.rar). In addition, keep in mind that it is not just about extension. The structure of RAR is too different from that of ZIP.