In season one, Zach is depressed by the sudden suicide of Mary Alice, so Paul puts him in a mental institution. During his stay, Julie sneaks in his room to speak with him but is asked to leave by a nurse. Zach later runs away and is found hiding in Julie's room by Susan and Mike who take him home. He and Julie then start dating. Susan speaks to Paul about Julie and Zach's relationship and is irritated when she thinks he is laughing at her but he insists it will not be a problem as he and Zach will soon be moving away. Zach, however, has other ideas and blackmails him to make sure they stay in Wisteria Lane as the police are asking questions about an old toy box that Zach once had as a similar one has been found with the body of a young woman inside. Whilst at the institution, Zach was diagnosed with clinical depression and a borderline personality disorder which makes his behaviour unpredictable at best so when Susan asks Zach not to see Julie for a while as she is concerned about how fast the relationship is progressing, Zach loses his temper so Susan promptly forbids him to see her ever again and throws him out. Julie initially rebels against this but after Zach scares her at his pool party, she doesn't see him again. In revenge, Zach blows her kitchen up before holding Susan hostage in the first-season finale. Zach then goes into hiding and reappears in the second season when Mike and Susan are looking for him. Susan tells him that she wants to help until he says he hopes he and Julie would reconcile. Susan, visibly shaken by this, suggests he go to Utah and find Paul and gives him money for the bus fare. Months later, after Felicia Tilman frames Paul for her murder, Paul begs Zach to ask his grandfather, Noah Taylor, for money to pay a lawyer, claiming it is for a car. Noah refuses, telling Zach that he would not inherit his fortune because of Zach's supposed lack of bravery. Wanting to prove him wrong, Zach turns off Noah's respirator and finds that he has inherited a vast fortune and no longer wants anything to do with Paul. Zach moves to his grandfather's mansion.