ZodUnion didn't import when using babel-jest

[typeetfunc]

I get an error when accessing nullable method when using babel-jest. I've discovered that the error is due to the ZodUnion file not being imported correctly.

TypeError: Cannot read property 'create' of undefined at ZodNumber.ZodType.nullable (node_modules/zod/src/types/base.ts:114:62)

if i use explicit imports, imports will work fine.

I created PR: #124