This is a special field for allowing multiple constraints of the same type on one field. This is mainly for RequiredIf constraints, not sure if it will work well with other constraints.
$validator = ZenValidator::create();
$validator->setConstraint(
$field,
new \Milkyway\SS\ZenForms\Constraints\Multiple([
new \Milkyway\SS\ZenForms\Constraints\RequiredIf($checkboxField, $state = 'checked'),
new \Milkyway\SS\ZenForms\Constraints\RequiredIf($textField, $state = '[value="Something"]')
])
);