Zambellas served as a corporate planner during the 1997–98 Strategic Defence Review before returning to operational command in 1999 as captain of the frigate and being deployed as part of Operation Palliser off Sierra Leone for which he received the Distinguished Service Cross in 2001. In 2001 he took the Higher Command and Staff Course at Shrivenham before becoming Deputy Flag Officer Sea Training, responsible for training Royal Navy and foreign warships and auxiliaries.