It's also clearly not intended as a password (why would you password protect a public zip archive?), but instead a "yeah you got us, but f** off" kind of message.
It may seem juvenile, but it is the kind of thing people do in an adversarial situation when they have no better hand to play, AKA they "got nothin'".
> why would you password protect a public zip archive?
I have no idea why they did it in this case, but I've seen it done to stop overly aggressive antivirus or antispam software from looking inside when the archive contains stuff likely to trigger false positives.
It may seem juvenile, but it is the kind of thing people do in an adversarial situation when they have no better hand to play, AKA they "got nothin'".