Complex sentence: Early in his career, Grosvenor worked as a freelance photographer for "National Geographic", completing 23 assignments for the magazine and its book division in counties such as Belize, France, Iceland, Spain, Tonga, and Turkey.
Split into simpler sentences: Early in his career, Grosvenor worked as a freelance photographer for "National Geographic", completing 23 assignments. Grosvenor subsequently worked as a freelance photographer, completing 23 assignments for the magazine and its book division in such countries as Belize, France, Iceland, Spain, Tonga, and Turkey.