Pode-se dizer que é uma carta de princípios, trazendo "a alma" do Python. Para ler esses princípios, basta entrar no shell do Python e digitar import this:
$ python
Python 3.8.8 (default, Mar 15 2021, 17:01:32)
[GCC 10.2.1 20201125 (Red Hat 10.2.1-9)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import this
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!
Aqui tem o Documento oficial: https://www.python.org/dev/peps/pep-0020/
Aqui tem o código fonte para esse import: https://github.com/python/cpython/blob/main/Lib/this.py
E aqui um texto meu sobre esse código-fonte: https://paulohrpinheiro.xyz/texts/python/2021-05-12-decifrando-o-zen-do-python.html