This paper presents reduction of ZnO in EPDM formulations and its influence on efficiency of cable isolation by measuring cure behavior, electrical and mechanical properties before and after ageing. These experiments were performed on EPDM formulations by changing three key variables in formulation (concentration of ZnO, type of peroxide and content of ethylene in EPDM). The theological characterization showed that replacing ZnO in EPDM with proper ethylene content (75%) with the lower content of ZnO (5 phr) in the recipes, resulted in lower cure time and higher scorch time and higher crosslinking density, which was further supported by Fourier transform infrared spectroscopy (FTIR). Mechanical properties before aging (elongation at break, tensile strength, and hardness) are greater with smaller content of ZnO. The value of percentage change of the properties after aging at 135 degrees C for 7 days, indicates that recipe D (Perkadox 14/40 (Di (tert-butyl peroxy isopropyl) benzene (DTBPIB)) peroxide cured EPDM has the best performance at tensile strength, and elongation at break. What is more, recipe D, containing 5 phr of ZnO exhibits the desired electrical performance. The paper provides sufficient experimental background to indentify the key physical aspects associated with each of the instabilities that occur at higher amounts of ZnO in formulation, and this in turns provides insight into different occurrences of each instability and how they can be minimized by reduction of ZnO in EPDM mixture.