theorem
  z = 0 implies z*' = 0
proof
  assume
A1: z = 0; then
A2: Rea z = 0 by Lm6,Th16;
A3: Im1 z = 0 by A1,Lm6,Th16;
A4: Im2 z = 0 by A1,Lm6,Th16;
  Im3 z = 0 by A1,Lm6,Th16;
  hence thesis by A2,A3,A4,Lm6,Th36;
end;
