What is the ruling on a Magian marrying a Christian woman?

Primary text

If a Magian marries a Christian woman and they present their case before a Muslim judge after embracing Islam, the marriage must be dissolved. Imam Ahmad stated that the separation must occur. This implies separation is mandated even if they do not bring the case before the Muslim authorities, because her religion (Christianity) is superior in standing to his (Magianism), thus prohibiting the union, similar to prohibiting a Muslim woman from marrying a Dhimmi (non-Muslim citizen under protection).