input: Write a python function to compare two complex numbers.
  assert compare_complex_numbers(complex(1, 2), complex(1, 2)) == 'z1 and z2 are equal'
  assert compare_complex_numbers(complex(1, 2), complex(2, 1)) == 'z1 and z2 are not equal'
  assert compare_complex_numbers(complex(0, 0), complex(0, 0)) == 'z1 and z2 are equal'
  assert compare_complex_numbers(complex(-1, -1), complex(-1, -1)) == 'z1 and z2 are equal'
output: def compare_complex_numbers(z1, z2):
      if z1 == z2:
          return 'z1 and z2 are equal'
      else:
          return 'z1 and z2 are not equal'