What is the ruling when an exception is made in a Zihar pronouncement?

Primary text

If a person declares, 'You are to me like my mother's back, if God wills' (Anta 'alayya ka-dhahri ummi, in sha'a Allah), or 'You are forbidden to me, if God wills' (Anta 'alayya haram, in sha'a Allah), nothing is binding upon him. This is because Zihar is an expiable oath, and the exception applies based on the general text concerning oaths.