The 28-year-old light-heavyweight - who scored a surprise victory over Cuba’s David Morrell last weekend - has a day job as a supply teacher between fights and he thinks both his professions require having a mental advantage.
He explained to The Guardian newspaper: “My mistake when I first became a teacher was that I was always happy. Never smile when you’re a supply teacher because the kids will rip you a new one. They’ll take the mick out of you.
"If you’re a supply teacher, they think they can do what they want.
"So I’ve learned to always have a firm and steady look, be sure about yourself, don’t be happy and say this is a great day because that’s when they try and take advantage.
“Before you get into the ring, you’ve got to mentally beat them and that’s how it is with students. You’ve got to let them know you’re going to be in charge.”
Zak's fight against David came following an injury to Callum Smith, and while he hopes to face the man he replaced next in a bid to become world champion, he has no plans to give up teaching because of the positive impact he can have on young people.
He said: "Usually, there’s one in the class who tries to mess you up and bring the others with them. But I take that student out and speak to them. They usually have an issue at home or they don’t understand the work and probably need one-to-one assistance. Once they see you can help them it changes.
"There have been times when I’ve had to bring out the deep voice to boys, 'Sit down, bags off the table or I’m calling the principal.’ But usually it’s calm.
“I also teach boxing to kids that have behaviour or special educational needs. It builds their confidence and communication skills. You need a lot of patience, but most of them are reaching their targets and enjoying it. It’s rewarding for me, seeing that I can change lives for good.”
But he admitted he gives a fake name to students at some of the schools he takes lessons at.
He said: "The only issue is once the kids find out who I am then the whole school knows. Luckily, as a supply teacher, I change schools. I did work for one school for a whole term and whenever I walked down the corridors all the students would jump up and say, ‘Hi, Mr Chelli.’ Or you’d hear them whispering, ‘He’s the boxer.’ So it gets a bit chaotic.
"I’ll say my name is Mr Jones and not tell them I’m a boxer because it can get crazy if they find out who you are.”
