Complex sentence: On 4 January 1918, "Schurz" was relieved of escort duty; and, after carrying the American consul from Puerto Cortes to Omao and back, sailed for Key West.
Split into simpler sentences: On 4 January 1918, "Schurz" was relieved of escort duty. She carried the American consul from Puerto Cortes to Omao and back, after which she sailed for Key West.