Mr. and Mrs. Glenn W. Ferguson of Shelter Harbor, R.I. and Munich, Germany, have announced the engagement of their daughter, Sherry Lynn, to Robert Bruce Zoellick, son of Mr. and Mrs. William T. Zoellick, Jr. of Naperville, Ill.

Miss Ferguson, a cum laude graduate of Swarthmore College, will receive a master's degree from the Fletcher School of Law and Diplomacy, Tufts University, this month. Her father, former U.S. Ambassador to Kenya and former president of the University of Connecticut, is president of Radio Free Europe/Radio Liberty in Munich, Germany.

Mr. Zoellick is also a cum laude graduate of Swarthmore College where he was elected to Phi Beta Kappa. He is presently in his final year at the Harvard Law School and in the master of public policy program at the Kennedy School of Government, Harvard University. Last year he served as special assistant to Assistant Attorney General Philip Heymann, U.S. Department of Justice. His father is affiliated with the Illinois Bell Telephone Company.

The wedding is planned for June 28 in Weekapaug Chapel, Weekapaug, R.I. In August the couple will depart for a year in Asia where Mr. Zoellick will be working as a Luce Foundation Fellow.