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

theorem
  z <> 0.F_Complex implies |.z".| = |.z.|"
proof
  reconsider z1=z as Element of COMPLEX by Def1;
  assume z <> 0.F_Complex;
  then z" = z1" by Th5;
  hence thesis by COMPLEX1:66;
end;
