Answer
Yes.
Work Step by Step
We know that for a rectangle to result in a square screen, $\frac{X_{max}-X_{min}}{Y_{max}-Y_{min}}=\frac{3}{2}$ must be true.
Here: $\frac{X_{max}-X_{min}}{Y_{max}-Y_{min}}=\frac{6-(-6)}{4-(-4)}=\frac{12}{8}=\frac{3}{2}$. Thus it is a square screen.