arg$ \frac {z_1 - z_3} {z_2- z_4} = \pi/2 $ or $- \pi /2$.

Question

I was reading Complex Algebra. I read some concepts about a rhombus whose co-ordinates are anticlockwisly $\;z_1 , z_ 2 , z_ 3 , z_4 $ . Then I understood that the following statements are true.

1. $z_1 - z_2 + z_3 - z_4 =0$

2. arg$ \frac {z_1 - z_3} {z_2- z_4} = \pi/2 \;\text{ or}\; - \pi /2$.

3. arg$ \frac {z_1 - z_2} {z_3 - z_4} = \pi$.

Can anyone please correct me If I have gone wrong anywhere.