Under neutron irradiation, recrystallized zirconium alloys, used as structural materials for Pressurized Water Reactor (PWR) fuel assemblies, undergo stress-free growth which accelerates for high irradiation doses. This acceleration is correlated to the formation of c-component vacancy dislocation loops lying in the basal plane. The growth behavior observed on some PWR fuel assemblies suggests that a macroscopic stress applied under irradiation could affect the c-loop microstructure and therefore influence the subsequent stress-free growth. In addition, some feedbacks show that in-service hydrogen pickup could also influence the fuel assembly radiation-induced deformation. The impact of an applied stress on c-loops has been studied on as-received recrystallized (RXA) Zircaloy-4 irradiated with 300 keV and 600 keV Zr ions at 573 K. An original device, specifically designed for the irradiation facility, applies a stress which relaxes during the early stage of irradiation. In these conditions, observations by Transmission Electron Microscopy (TEM) reveal no effect of the initial applied stress on c-loops. However, when the stress is applied when c-loops are already created, c-loop growth is affected. Moreover, 2 MeV proton irradiations performed on as-received and pre-hydrided M5 (M5 is a trademark of AREVA NP registered in the USA and in other countries.) and RXA Zircaloy-4 materials were conducted at 623 K. For both grades, the c-component loop evolution with dose is examined and compared to neutron irradiated microstructures. As for neutron irradiated materials, the c-loop density in Zircaloy-4 is higher than in M5. For pre-hydrided RXA Zircaloy-4 the effect of hydrogen is not significant since the loops are already present in high density. On the other hand, TEM observations on pre-hydrided M5 highlight that c-loop density is higher, far from hydrides, than without pre-hydriding. Furthermore, a high c-loop density is observed in the surrounding of hydrides partially or fully dissolved. To explain these observations, the role played by hydrogen in solid solution and as precipitated hydrides is discussed.