Some bundlers have stricter treeshaking requirements than others, and Webpack (and Turbopack) used by Next.js don't seem to be able to treeshake Zod imports unless they're formatted like import * as z from 'zod'.

See this comment for more details: colinhacks/zod#4433 (comment)

Using a bundle analyser, I can see that Next.js projects using t3-env also include all of the zod locales because the imports are currently formatted like import { z } from 'zod'. I propose updating these imports to allow more bundlers to treeshake correctly.