I've never used these websites much, and I have the same problem with the buttons as you, trying with different browsers. Additionally "download as zip" does nothing because it apparently requires a premium account. Perhaps their help or faq has some answer. I wonder if it's now mandatory to register or install something... I've heard some people use programs such as
JDownloader.
In any case you would need to download all files (although the two smaller ones whose extensions don't start with r are optional information files) into the same folder, and then open the .rar one, having installed 7-zip or WinRAR (links
here)
If text is too small on your browser, try pressing Ctrl +. You could also contact 4shared to report accessibility problems, although this may not help a lot in the immediate term.