Keep in mind that while AES is good, strong encryption, a weak password makes any encryption easy to crack. Also, there are a number of zip cracking software suites out there, some are very effective. They use imperfections in the encryption implementations (almost never the encryption algorithm itself) to gain significant advantage over simple brute force cracking.

Brute force cracking can be done very effectively if you throw enough horsepower at it. Using Amazon EC2, most passwords can be cracked for less than $100. Often far less than $100.