Sorry if it's too inconvenient to download the individual files, but I would have to put up every soundtrack twice - in single files and in one zip-file.
But using download managers like GetRight or FlashGet will do the trick. GetRight for example adds a nice tool to the right-click-menu inside your browser, eloquently called "GetRight browser". This shows all the files in the current html-file and let's you select which ones to download. It takes only a few clicks from there on, selecting a directory and starting the download.
Or is there a way to get access to the contents of a zip file via java-script or some other fancy web-language? By this I would only have to upload the zip-files, and the user can choose whether to download the whole thing or individual files from it.