There's no need to extract the whole zip file just to see what's inside. Just drag files and folders from all around your hard drives, disks, or network places into your new zip file. Because first copying them into a temporary folder is really lame.
Drag in new or updated files, remove any file or folder from the archive, or move files around inside the archive. If you only need this one file from your archive, you don't have to extract the whole thing and remove all the other files. Simply drag those files you need out into the Finder. Strip Mac specific files and resource forks from zip files and tar balls for best compatibility with less powerful systems like Windows or Linux.