Complex sentence: He then was selected as the State Department's coordinator for the Conference for Security and Cooperation in Europe (now OSCE) and later as Deputy Presidential Special Advisor for Bosnia Implementation, working to put into place the Dayton Accords.
Split into simpler sentences: He then was selected as the State Department's coordinator for the Conference for Security and Cooperation in Europe (now OSCE). Jeffrey later served as the Deputy Presidential Special Advisor for Bosnia Implementation, working to put into place the Dayton Accords.