If I just want to be able have a quick read-only look into a tcz archive I simply loop mount it.
For this I create a temporary directory with mkdir tcz-extr ; sudo mount EXT.tcz tcz-extr. The files of the archive are all available via the 'tcz-extr' directory. After use I simply un-mount and remove the directory with umount -d tcz-extr ; rm -rf tcz-extr. All this works with the TC / MC base, i.e. without any further extension.
If you want to really extract all the files you'll need the squashfs-tools-4.0.tcz extension and use the 'unsquashfs' command.