Why do they need that many z8c? 075 is only using it, because there is no alternative. Longer term, most the air wing will be other helicopters.
Z8C will be deployed in large numbers until there is sufficient Z20J have been inducted into service. I do not see Z8C as alternative to Z20J but rather that they will complement each other in different air lifting roles in different situations.
I expect both Z8C and Z20J will be deployed in several different mixed numbers depend on the type of mission and environment. Example in first phase of a beach assault action, Z20J will be deployed due to their small size thus smaller target and (may be) more advanced ground fire evasion/warning devices. Loss of Z20J to ground fire means smaller casualty numbers.
Z8C has larger lifting capacity and can carry more marines, and are essential for quick transfer of large quantity of material and manpower from ships to shore. They are likely to be deployed in secured areas, and will remain an important part of airwing on type 075.
I think it is likely this helicopter will eventually be replaced by a combination of the Z-20 and Z-8L on the Type 075.
IMO, Z8C was developed specifically for type 071 and 075. Z8L has been observed only in PLA ground forces service. As to why we have not seen Z8L in PLAN service and we have not seen any navalised Z8L with folding rotor blades and folding tail, I think may be they prefer Z20J instead.
Also, IMO Z8L's development was mainly due to requirement for quick embarkment and dis-embarkment of soldiers and widen cabin for mountain cats and other smaller vehicles. No doubt its reduced height is better suited for hangars of destroyers and LPD/LPH but the navy seem to have made up their mind in choosing Z20J.
