Ah, ok. Quoting from that page: "Zlib support in PHP is not enabled by default. You will need to configure PHP --with-zlib[=DIR]". This basically rules this out, since seamless zip handling is not possible with out of the box PHP.
It's not enabled by default, that's true. But neither is GD or ImageMagick: "You will need to compile PHP with the GD library of image functions for this to work. [...] To enable GD-support configure PHP --with-gd[=DIR], where DIR is the GD base install directory." We could enable downloading if zlib is there (which it is on probably 95% of all production sites). Otherwise, the user has to do it manually (links are shown during installation) or download an uncompressed version (about 500 kB for a complete 4.7 translation). I think that's a fair compromise. Konstantin Käfer – http://kkaefer.com/