Thank you for pointing out that problem and suggesting enclosing the entire URL in quotes which accommodates both environments.

However, since quotes are not commonly used in regular pip installations, I am a bit concerned that it might actually confuse people who don't usually use zsh. I am thinking about what to do with the README. Perhaps, it would be a good idea to add a separate note suggesting to try using quotes if the installation doesn't go smoothly. This is quite a subjective matter, so it's a bit difficult to decide. I'll think about it a bit more before making a decision. Anyway, thank you very much for your feedback and the suggestion for improvement!