The detail expression that takes advantage of the large size of the kit, and the paint expression that gives a sense of scale, are effective.
The base is also composed without disturbing the presence of the main body of Zaku, weaving in and out of the height difference, and the shell casings at the feet add an accent to the diorama.
Because it is a rather simple construction as for the main body of Zaku, it would be good to add detail to the head, shield, arms, etc., commensurate with the scale.