Zach is a young Caucasian male with midlength combed brown hair and green eyes. He's shown to be fairly pale, tall, and clean-shaven with a fit, athletic frame. His shown attire is that of a rich prep, a buttoned pink shirt with flannel shorts and shoes.
His kill attire is similar to Dexter's, a tight dark black longsleeved shirt complete with dark pants and shoes, along with black gloves.
Zach is an eerie yet inquisitive youth, who immediately inserts himself into the questioning of his father by detectives involving the death of a woman he was sleeping with. When he approached, he had a gaze that suggested concern of what his father might say or what the police know...suggesting that he in fact killed the girl or had some involvement (which he did). He later approaches Dexter, who was on scene, questioning him about his knowledge and analysis involving the crime scene...potentially trying to learn what they know.
In reality, he is a psychopath whose murderous impulses have developed under unknown circumstances. He is vastly endorsed in the sight of blood, taking pictures of crime scenes and "touching up" the photos to breathe more life into his "art". When he kills someone, he describes the feeling as a heavy weight being lifted off his chest and feels that he finally has control over something. Unfortunately, his urges are somewhat chaotic. While his tutor Dexter Morgan grew up from his early childhood with Harry by his side, Zach is a young man having only just met a teacher. His psychopathic instincts have sewn themselves deep in his mind, making his urge to kill intensely strong and potentially stronger than his own willpower.
After speaking to a witness who recognizes Zach driving in a porsche nearby during the time Norma Rivera was killed, Quinn pursues him, but is told to back off by Deputy Chief Matthews after the witness recants his confession. Quinn, however, continues to tail him, hoping to find something to prove his guilt.
Dexter's ApprenticeEditAs Quinn vets Zach, so does Dexter, eventually finding images of Norma, which Zach took right after bludgeoning her to death. As Dexter sees Zach following his father in an attempt to kill him, he intercepts and put him on his table. Upon realizing that Zach is just like he once was (except without a guide), he decides not to kill him, but to take him on as his apprentice, teaching him the Code of Harry.
Eventually catching images of Quinn stalking him, Zach files a complaint to the police department and demands that Quinn back off, which he is ordered to do by Matthews and Batista. Zach is enthusiastic to go for a kill, but is told to control his urges for a while, so things can go more smoothly. Eventually, he grows tired of Dexter holding him back and goes to his apartment, repeatedly knocking loudly on his door. Dexter's neighbor Cassie notices this and tells Zach that he's not home, to which Zach gets even angrier and insults him. Cassie is shown dead later on, and Zach's blood at the crime scene apparently points to him as the killer.
Shaun DeckerEditDexter, knowing that he cannot incriminate Zach to the police since he knows too much about him, covers up the evidence pointing to him and searches for Zach himself, in order to kill him. Upon finding Zach, Dexter chastises him for allegedly having killed Cassie. However, he realizes soon afterwards that someone else tried to frame Zach for Cassie's murder (possibly The Brain Surgeon) and that Zach was stalking a killer named Shaun Decker the whole time. After seeing Shaun's body, Dexter helps Zach cover his tracks and the two resume their relationship as teacher and student. This relationship is short-lived, however.
DeathEditAfter Dexter returns home from a romantic encounter with Hannah McKay, he discovers Zach slumped back in his chair with his eyes open and motionless. A song is playing in the background from a phone, "Make Your Own Kind of Music", while Dexter approaches the body and spins the chair, revealing that the back of his head has been removed, with his brain cut open and a portion excised (the anterior insular cortex). Zach's body was wrapped in black plastic, kept intact and dropped into the sea while Dexter was out on the Slice of Life. After his death, Dexter resumes his hunt for Zach's killer and it isn't until episode 10 that when Dexter is monitoring a man named Oliver Saxon's recent computer activity, he comes across a video of the latter murdering Zach with a bonesaw off-screen, proving that Saxon is the true Brain Surgeon.
- Zach is officially Dexter's third apprentice, the first two being Miguel Prado (whom he later killed) and Lumen Pierce (who retired from killing).
- He may be the youngest psychopath on the series, next to Jeremy Downs.
- While Dexter feels he's nothing like Zach, they are fairly similar in physique and interests. Zach's appearance also somewhat mirrors Dexter's, though at a much younger age, and somewhat makes him like Peter Thorton, who became the "Dark Echo" of Dexter.
- Zach is one of the few characters dumped in the ocean who were not killed by Dexter or by anyone affiliated with him. The act of dumping him was to get rid of the body, avoiding another investigation into The Brain Surgeon and removing evidence of him being left at Dexter's house.
- He is the only apprentice of Dexter to be killed by the Main Antagonist (The Brain Surgeon).
- He is the only victim of The Brain Surgeon shown to be killed while he was still conscious. The other victims were first killed before their anterior insular cortex was removed postmortem.