Zarf, a transgenderrock star, is found to have had pictures of Zach's late mother in his London apartment. Zach is also haunted by the memories of his mother's death and thinks that is somehow resulting in the Fusion murders. Zach is then convinced that Zarf is the killer and Zach stops at nothing to prove this. However, the serial killer is later revealed to be Alexander Cambias, Sr., Zach's biological father, by the terror name of Satin Slayer. Zach goes to Las Vegas with Kendall and has his father's grave opened. They are shocked to discover that the casket is empty. Zach's father is still alive.
After Alexander is apprehended, he plays mind games with Zach and one of them is naming his wayward son the new chairman and CEO of Cambias Industries. Zach turns it down on the spot, but Alexander tells him that if he doesn't take over the company, it and all of its assets will be turned over to a defense fund to provide legal services for accused rapists. He also threatens the livelihood of everyone Zach loves: Kendall, Bianca Montgomery, Miranda Montgomery and Spike Lavery, because Fusion Cosmetics will be shut down. Zach talks his father's terms over with Kendall and Bianca, and they convince him that the company can be a force for good. Zach takes it on. He is now father to Ian Slater, who was prematurely born.
Zach was also father of Ethan Cambias due to an affair he had with Hannah Nichols many years ago. Ethan never really forgave his father for abandoning him before birth. Ethan and Zach were just starting to get close when Ethan was killed in an explosion in 2006. Zach got to the hospital too late and broke down in tears when he found out Ethan was dead.
Became best friends while they battled for their lives trapped together in a bomb shelter, the only two in the dark and desolate hole. Started out as enemies, emerged with a profound respect for each other.
Almost killed Kendall (he was trying to kill his wife, Babe Carey Chandler) while Kendall was pregnant with Spike, which caused her to go into premature labor.
Kendall slept with Aidan while Zach was trapped in the bomb shelter and thought to be dead. Zach has recently forgiven Kendall but still holds a grudge against Aidan.