Most common site of zygomatic arch fracture is:

The zygomatic bone usually fractures in the region of the  zygomaticofrontal  suture, the  zygomaticotemporal suture and the zygomaticomaxillary suture. It is unusual for the zygomatic bone itself to be fractured, but in extreme violence, the bone may be comminuted or split across. Most common site of zygomatic arch fracture is posterior to Zygomaticotemporal suture. The isolated zygomatic arch fracture may occur without displacement of the zygomatic bone. Ref: Oral and maxillofacial surgery , Neelima Anil Malik 4th ed page no 534