Just this, always.

https://www.theonion.com/any-idiot-could-have-come-up-with-t...

Almost as good as the ole classic dropbox comment https://news.ycombinator.com/item?id=9224

I wish whatever you were doing had peaked. We need less of it.

In fact, this is a good question. As described in this thread (a transposition cipher layered over a substitution cypher) this is something easily crackable. And in fact, in the video we see an example of that easy automated cracking, once they'd figured out a roadblock issue.

They touch on the actual difficulty in the video, but it obviously bears repeating - errors. Zodiac apparently screwed up in a few places, dropping a characters, misspelling words (maybe intentional), and so on.

These days we tend to think of cyphers as mechanically perfects, and it's easy to not realize that this was created by an amateur with pen and paper.