The rim of Zeno is slightly distorted and has received some erosion due to subsequent impacts. There is a depression in the surface attached to the eastern rim, forming a bulging extension. Small craters lie on the southern rim and across the interior of the northern wall. The crater Zeno B is attached to the exterior of the southwestern rim, and the distorted Zeno A is attached in turn to the western rim of Zeno B.
By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Zeno.