Complex sentence: He was the chaplain of Juan Bautista de Anza's expedition that explored Alta California from 1775 to 1776, and authored the diary "With Anza to California", the principal account of the expedition.
Split into simpler sentences: He was the chaplain of Juan Bautista de Anza's expedition that explored Alta California from 1775 to 1776. Font authored the diary "With Anza to California", the principal account of the expedition.