Compressing data sent from the browser to the server is not supported in browsers.
You need to find a workaround using the client language (perhaps an implementation of JavaScript GZip or a Java applet or ...). Be sure to visually show the user what the browser does and why it takes some time.
I don’t know the scope of your application, but on company websites you can simply limit input to compressed files. Ask your users to download .zip / .7z / .rar / .... files.