On the Argand Plane,
Z lies on the circle with centre O(0,5) and radius 1
Z1 lies on the circle with centre O'(5,0) and radius 1
For |z - z1| to be maximum z should lie at H and z1 should lie at G.
<QOG = 45°.
Therefore point z1 with both the properties is 5+1/√2 - i/√2