http://en.wikipedia.org/wiki/Comparison_of_web_browsers
For February, 2007
IE6 - 49%
IE7 - 29%
Firefox - 14%
Safari - 5%
Opera - 0.8%
Netscape - 0.7%
Mozilla - 0.2%
1 - it's only 80% for all IE
2 - it's only 30% for IE 7 (no corrupted zip with IE 6)
3 - Fortunately, it's not because a monopolistic company decide something that it became the norm, even when it's called Microsoft. That's why we are beginning to have CSS compliance, that's why we still have Java, that's why there are still some computer users who don't find "normal" to have to update their anti-virus several time a day.
4 - what are "standard zip apps", anyway ?
computing axiom: it's not because it doesn't work on your computer that it's broken. It may very well be (and often is) your computer that is the cause of the problem.