forensics
The regular expression is given, which makes the list of password.
By using bruteforce, we can get the real password. After cracking the zip file, there is hint.txt and archive.zip.
hint.txt is also a regular expression, and archive.zip needs password!
This pattern repeats 999 times, and finally we can get the flag.txt!
utflag{bean_pure_omission_production_rally}