Complex sentence: In 1951, he was assigned as an assistant parish priest in New York City after which he was appointed in 1956, at the age of 30, as the vice rector of the Catholic University of Puerto Rico.
Split into simpler sentences: In 1951, he was assigned as an assistant parish priest in New York City. In 1956, at the age of 30, he was appointed as the vice rector of the Catholic University of Puerto Rico.