Which of the following does not give oxygen on heating?

KClO3, Zn(ClO3)2 and K2Cr2O7 on heating give oxygen whereas (NH4)2Cr2O7 does not give oxygen on heating.
2KClO3 --MnO2--> 400°C 2KCl + 3O2↑ (Lab method).
4K2Cr2O7 heat --> 4K2CrO4 + 2Cr2O3 + 3O2↑
(NH4)2Cr2O7 Δ --> N2(↑) + Cr2O3 + 4H2O