Zygoma reduction has caused volume loss and face to sag, would a facelift fix this?

While a facelift might help, it will not compensate for the loss of volume.  If you go this route I would suggest adding a filler such as Voluma, Restylane Lyft, or Radiesse in the area of the zygoma/midface.

Even giving general advice to your important question would be very difficult without photos and knowing precisely what was done in your initial operation. Many good options are available and finding the one that best suits you requires a consultation with your original surgeon or another recommended surgeon. Best regards.

This is a complicated question, as there are many variables to consider.  It is possible that re-suspending the fat/muscle/skin of the midface is all that is needed.  Revisit your concerns with your surgeon, or seek an in-person consultation with a plastic surgeon specializing in facial surgery in your area.