In the low-temperature (T < 304K) phase both CH3 and NH3 groups execute threefold reorientations, the former in a symmetric potential well and the latter in an asymmetric potential well. The relaxation results in the rotating frame reveal a defect motion in this phase. Additional defect motions, superimposed on fourfold reorientations of chains, are present in phase II (317 K < T < 369K). In phase I (T > 369 K), melting of chains occurs. Although hydrogen bonding is stronger in (C13H27NH3)2ZnCl4 than in (C10H21NH3)2ZnCl4, fast fourfold motions of chains are present at lower temperatures in the former compound. Melting of chains occurs at approximately the same temperature in these compounds.