"Z. robustus" is known from about 80% of the skull. However, no complete articulated skull is known, and most of the bones do not overlap and are found in isolation. Weishampel "et al." found that these likely represented one individual, as the bones were from the same formation and are the same colour. Four individuals were identified by Nopcsa for "Z. robustus", and from these it can be seen that there is skeletal variation in the species. Like with the cranial material, vertebrae of "Z. robustus" are often found isolated. All regions of the vertebral column are represented in the fossil record, although no sternal plates have been found yet. The sacrum includes three vertebrae, with two sacrodorsals (dorsal vertebrae in the sacrum) and three sacrocaudals (caudal vertebrae in the sacrum). The limb and girdle bones are also well represented, with only the hands (manus) and feet (pes) mostly lacking.