A zoeaaf is a zouave, a member of the infantry forces of the Papal states.
In the mid 1800s, the Papal states were threatened by forces in Italy who wanted all the states to join under one nation. In 1860, pope Pius IX sent out a call to young unmarried Catholic men to join the infantry force and defend the papacy.
The zouave papal infantry force existed from 1861 and 1870. The men volunteered for a period of two years, and some extended. In total, about 11,000 men enlisted with the zouaves, including over 3,000 men from the Netherlands. They gathered in Oudenbosch in Noord-Brabant before going to Italy. Oudenbosch now houses the Zouave Museum.
The first place to look for zouaves is the zouave register at the Zouave Museum website. This will tell you if your family member served. The museum has the enlistment registers and personal files on these enlisted men, which requires a visit to Oudenbosch.