If the zsh situation is similar to bash (as it seems to be, from the link you posted), then then problem is that zsh provides completions through readline commands only.
This makes it hard to access them from Emacs. The bash-completion package mentioned in the blog post does that, but it’s a tricky solution, and not super robust in my experience…
There is a thing which provides zsh completions. It’s zsh. If that’s what you’re wanting, then maybe don’t stop using it?
If the zsh situation is similar to bash (as it seems to be, from the link you posted), then then problem is that zsh provides completions through readline commands only.
This makes it hard to access them from Emacs. The bash-completion package mentioned in the blog post does that, but it’s a tricky solution, and not super robust in my experience…