Complex sentence: The Reformed Church in America was the greatest Protestan denomination with 4,500 members in 11 churches followed by the United Methodists with 3,600 congregants and 20 churches, the thirds is the Christian Reformed Church with 10 churches and 2,600 members.
Split into simpler sentences: The Reformed Church in America was the largest Protestant denomination with 4,500 members in 11 churches, followed by the United Methodist Church with 3,600 congregants in 20 churches. The third largest Protestant denomination is the Christian Reformed Church with 10 churches and 2,600 members.