Synthesizing rhymes with:
deemphasizing, emphasizing, fantasizing, overemphasizing, publicizing, romanticizing, criticizing, deemphasizing, downsizing, emphasizing, exercising, fantasizing, overemphasizing, politicizing, publicizing, romanticizing
Synthesizing sounds like:
saint-saens, sanitizing, smithson's, smithsonian's, snatching, snitching