well,of course they´re not really infected so to open these zip-files isn´t dangerous, but virus scanners pick up any files that may cause harm to them too ("virusname hacktool"), you can exclude these files from the scan (depends on your antivirus application). But files like trojans or virus generators can´t be handled this way, you have to turn off your virus scanner completely. I guess you´re a beginner so the best is you use an extra computer for experiments with such files to be on the safe side. if you´re not having this opportunity be very careful what you do, some files may include a live virus as an example or something like that, so first check the READMEs if there is one included...
