Diphthong rhymes with:
adlong, berrong, bogelsong, boipatong, bushong, deshong, dishong, dulong, ewong, foglesong, ganong, groshong, haifong, hartong, herlong, hindelong, hongkong, hopalong, nifong, oblong, oolong, pingpong, shiong, susong, vogelsong, wilfong, wiltfong, wysong
Diphthong sounds like:
davidian's, davidians, debating, debuting, defeating, deviating, deviations, devoting, dividing, doubting