I've created some crazy types with zod since v3 released, these look like really interesting changes for v4.
I've been bit by performance issues, and even a few issues where I just couldn't infer types, with some of the more complex schemas I tried to define, especially with multiple .extend() and .omit() calls.
The zod-mini library looks particularly interesting. I don't mind the more functional approach with nested functions rather than chaining. Reminds me of ramda, that library is pretty massive but still easy to tree shake since everything is functional.