There are several issues Christians and Muslims can unit to tackle, but I’ll pinpoint two:
1) Intermarriage: it is almost impossible for Muslim parents to allow their daughters to marry a Christian man. If the females insist to marrying a Christian, they would face rejection or abandonment.
2) Freedom of worship: I’ve seen in most Muslim countries that it’s almost impossible to find church(s) or the freedom of Christians to assemble in worship, unlike in Christian countries.
These are two key issues that Muslims and Christians need to sit at the drawing board and find remedy to.
It would be unfair to deny female Muslims from marrying Christians men and not only Muslim brothers marrying our Christian sisters and converting them to Islam; whereas Christians should not be denied freedom of worship in Muslim nations and vice versa.