How to do sub field validation?

  const form = useZeroAppForm({
    defaultValues: {
      create_user: createUserDefaultValues,

      create_vendor: createVendorDefaultValues,

      vendor_documents: {},
    },

    validators: {
      onSubmit: zod.object({
        create_user: createUserValidator,
        create_vendor: createVendorValidator,
        vendor_documents: zod.object({}),
      }),
    },
  });