Reviewing the information in the online posts here, and consulting other sources, I would think that the alleged "daughter of the Sultan" that Jan Jansen was involved with/married to would NOT be a daughter of Moulay Zidan En Nasir for the following reasons:
1. The Republic of Sale is located in the area of the northern Kingdom of Fez (not Zidan's southern Kingdom of Marrakesh); 2. The event occurred most likely after 1616, the earliest year I have found reference to the existence of the Republic; 3. The event occurred in or before 1626 when the Republic appears to have dissolved, temporarily at least; and 4. After 1626 but before 1630/31, Jan Jansen apparently relocated to Algiers for a number of years.
Between 1616 and 1626, the northern Kingdom of Fez was ruled first by the Sultan Abdullah II (1613 - 1624) and then his son Abd El Melik III (1624 - 1626). The daughter would more likely be that of either of these two Sultan's rather than a daughter of Moulay Zidan En Nasir, "Sultan" in the Kingdom of Marrakesh from 1610 - 1627/28 where his power was very limited due to the presence of powerful marabouts. see for example: Eleanor Hoffman's "Realm of the Evening Star, A History of Morocco and the Lands of the Moors" (Philadelphia: Chilton Books, 1965) pp. 135 - 150.