The actor's troubled character is sectioned in the coming days after going wandering on the moors in a confused and delirious state.
Speaking on This Morning today (May 9), Halliwell promised a realistic portrayal of mental health issues as Zak receives treatment in hospital.
Asked where the storyline is heading in the long term, he replied: "I'm not totally certain myself, but Stuart Blackburn the producer likes the idea of consequences of actions.
"Often in soap it gets wrapped up in a week and everyone's shaking hands again. He's very much against that, so I think it'll be a long process - as in life. People don't just get over nervous breakdowns just like that."
Halliwell also discussed the help he has received from the Emmerdale team while working on the storyline.
He said: "The writers have obviously researched a lot of the stuff. We were lucky to have an actor playing the doctor - when [Zak] actually gets taken in - who also worked as a psychiatric nurse.
"So he was very good when I'd say, 'Was that right?', 'Am I doing that right?' He was really like an unpaid advisor through some sequences!"
Emmerdale airs weekdays on ITV1.