Answer:
 AD = 79
 ZB = 86
Step-by-step explanation:
If Z is at the intersection point of the perpendicular bisectors of the sides of the triangle, it is the "circumcenter", so is equidistant from the vertices.
 ZB = ZA = 83
If D is the midpoint of AB, then ...
 AD = AB/2 = 158/2 = 79