Complex sentence: Arthur C. Parker, Secretary of the Society from 1911-1915, was one of McKenzie's closest friends among the organization's leadership, and working together they navigated internal politics and developed a lasting friendship.
Split into simpler sentences: Arthur C. Parker, Secretary of the Society from 1911-1915, was one of McKenzie's closest friends among the organization's leadership. Working together they navigated internal politics and developed a lasting friendship.