reserve a,b,c,d for Real;
reserve z,z1,z2 for Complex;

theorem Th67:
  |.z1.| / |.z2.| = |.z1/z2.|
proof
  thus |.z1.|/|.z2.| = |.z1.|*|.z2.|" by XCMPLX_0:def 9
    .= |.z1.|*|.z2".| by Th66
    .= |.z1*z2".| by Th65
    .= |.z1/z2.| by XCMPLX_0:def 9;
end;
