Basilar Skull Fracture: Given the symptoms of left-sided zygomatic and periorbital hematoma, epistaxis, and mild confusion following an assault, a basilar skull fracture is highly plausible. The mechanism of injury and the combination of facial trauma with neurological symptoms (mild confusion) support this diagnosis.

Orbital Fracture: The presence of periorbital hematoma could indicate an orbital fracture, which is a common injury in facial trauma.
Nasal Fracture: Epistaxis (nosebleed) following an assault could be due to a nasal fracture, which is a frequent injury in such scenarios.
Concussion: Mild confusion could be a sign of a concussion, a type of traumatic brain injury caused by a blow to the head or body, a fall, or another injury that jars or shakes the brain inside the skull.

Intracranial Hemorrhage: Although less likely than some other diagnoses, an intracranial hemorrhage (such as a subdural or epidural hematoma) is a potentially life-threatening condition that must be considered, especially with symptoms of mild confusion and a history of head trauma.
Cerebrospinal Fluid (CSF) Leak: A basilar skull fracture can lead to a CSF leak, which may not be immediately apparent but can have serious implications if not addressed.
Retinal Detachment: Trauma to the eye can cause retinal detachment, a medical emergency that requires prompt treatment to preserve vision.

Carotid-Cavernous Fistula: This is a rare condition where there is an abnormal connection between the carotid artery and the cavernous sinus, which can occur after trauma. It might present with symptoms like exophthalmos, chemosis, and bruit.
Traumatic Optic Neuropathy: This condition involves damage to the optic nerve due to trauma, which can result in vision loss. It is less common but should be considered in the differential diagnosis of a patient with significant facial and head trauma.