Born in Addifini, eparchy of Asmara, Ethiopia, on August 25, 1921, Cardinal Tzadua studied at the Seminary of Cherer. He was prevented from finishing his studies due to the outbreak of civil war. On March 12, 1944, he was ordained. He was immediately appointed Vice-Parish Priest of Asmara Cathedral and Director of the Cathedral school, which under him became one of the city's finest. In 1953, he earned a degree in Classics from Asmara's Italian high school Ferdinando Martini. Obtaining a scholarship to the Catholic University of Milan, he left for Italy, graduating in 1957 in Political and Social Sciences, and in 1958 in Law. He was elected Titular Bishop to the Church of Abila di Palestina on March 1, 1973, promoted Archbishop of Addis Ababa on February 24, 1977, and elevated to the cardinalate by John Paul II during the Consistory of May 25, 1985. Tzadua was a member of the Congregation for Eastern Churches and of the Pontifical Council for the Interpretation of Legislative Texts.