Famous for his involvement in the Congress of Racial Equality's Freedom Riders civil rights initiative, Zwerg was the 1961 recipient of the Southern Christian Leadership Conference's Freedom Award.
Before becoming a Freedom Rider, he was a student in the sociology department at Beloit College.
In the years following his civil rights activism, he studied at Garrett–Evangelical Theological Seminary and became an ordained minister.
He grew up in Appleton, Wisconsin as the son of a dentist. He later lived in Arizona and New Mexico with his wife Carrie and the couple's three children.
Civil Rights leader Martin Luther King Jr. encouraged Zwerg to pursue a career in the ministry.