Let z=x+iy:
|(x-2+iy)|/|(x+2+iy)| <= 1
[(x-2)²+y²]/[(x+2)²+y²] <=1
Since the denominator is always positive (both variables are squared) then it is okay to multiply the denominator out with an inequality.
(x-2)²+y² <= (x+2)²+y²
-8x <= 0; x>=0.
I think that's right but I may have done something wrong somewhere, I haven't done these in quite a while.