reserve z,z1,z2,z3,z4 for Element of F_Complex;

theorem
  z1 <> 0.F_Complex & z2 <> 0.F_Complex implies z1" / z2 = (z1 * z2)"
proof
  reconsider z19=z1,z29=z2 as Element of COMPLEX by Def1;
  assume
A1: z1 <> 0.F_Complex;
  assume
A2: z2 <> 0.F_Complex;
  then
A3: z1 * z2 <> 0.F_Complex by A1,VECTSP_1:12;
  z1" = z19" by A1,Th5;
  hence z1" / z2 = z19" / z29 by A2,Th6
    .= (z19 * z29)" by XCMPLX_1:221
    .= (z1 * z2)" by A3,Th5;
end;
