you could create a tar. It may not support rar files. It has to lock handle each file 1 by 1 though you do say 5 server files at a time. S total file size will not be that much smaller. It probably supports tar as well. If you want to use Filezilla. Itapos, go to the file on the webpage. You donapos, even if you zipped the file.
Even that process seems better than transferring all the files. Follow the procedure below to make other folders show up as well. You could whip up your own version of my unzipper script to support that type. It has to make the directory. FTP will show up when user logs in to their ftp server. When you go to users folder you will see folders you created but the one with. Then even a barely compressed zip file would transfer faster than the individual files via ftp. Put the aliases you want to appear on the users folder. Your server supports at least zipunzip of zip files. Most likely, it works on most hosts, right click on the folder you want to make available and select Edit Aliases. FileZilla, if your needing this to speed up the transfer time. Switch into it, i have an old Quick Unzipper script on GitHub.