There isn't "no way" to use ZIP or RAR archives on the 770. I've said as much several times on these forums and I'll say it again.

If you want a command-line version of unrar, download this archive. It contains one file, which is unrar compiled for ARM. It runs fine on my 770 under Xterm.

Presumably you can find a command-line binary for unzip from one of the various ARM flavors of Linux, as free unzip code is readily available. FBReader supports Zip files internally, for example.

If you want a GUI to access ZIP or RAR files, that's another thing. I agree, it would be nice if the File Manager could support archive files of this kind (and TAR files as well) but it's not exactly a standard OS-level feature for a handheld device like the 770.