less than or equal to formula for complex numbers

[Lukas Reichlin]

Dear Octave Community

The Octave manual defines for complex numbers the following ordering: z1 < z2 
if and only if

        abs(z1) < abs(z2) || (abs(z1) == abs(z2) && arg(z1) < arg(z2))

Now I'm looking for the formula for z1 <= z2:

Could it be

        abs(z1) <= abs(z2) || (abs(z1) == abs(z2) && arg(z1) <= arg(z2))
or      
        lt (z1, z2) || eq (z1, z2)

or something completely different?

The reason why I'm asking is that I want to implement something similar for 
quaternions.

Thanks for any hints!
Lukas