Honestly, my .zshrc file started out as a .kshrc file that was passed down to me by an older developer about 20 years ago, when I was still in university. I've added and removed a lot of things over the years, but there are still a few parts of it that I don't totally understand, simply because they work and I've never had a reason to think about them. The guy I got it from, in turn, got his from someone else.
In the old days, I had a .fvwm2rc config file that I got from my boss in the university computing center. I had no idea how it worked! And neither did he -- he got it from a professor when he was in university.