For x1,x2,y1,y2ϵR, if 0 < x1 <x2,y1=y2 and z1=x1+iy1,z2=x2+iy2 and z3=12(z1+z2), then z1,z2,z3 satisfy
The coordinates of the mid-point of the line segment joining two points P(X1, y1, z1) and Q(x2, y2, z2) are: