Florian Zeller has made a speciality of disorienting his audiences. Last year, the skilfully blurred timeline of The Father, based on his own Alzheimer’s-inspired play, landed him an Oscar for best adapted screenplay, along with a best actor award for Anthony Hopkins. Yet the French playwright and director’s new work, The Forest, about to have its world premiere at Hampstead theatre in London, may be his most disconcerting yet.

“I tried to create a maze,” Zeller says over Zoom from his home in Paris. On stage, scenes repeat themselves with micro-variations: different actors may or may not be playing the same person. “The goal wasn’t to lose people in this forest. It was to put them in a confusing situation and let them piece it together.”

For such a labyrinthine storyteller, Zeller appears to conduct his career with unerring clarity. He has been described as a hit machine: from The Father, which put him on the international map after much success at home, to The Son, now being turned into a film starring Hugh Jackman and Laura Dern, nearly everything he has written in the past decade has turned into gold. When I ask Jonathan Kent, who is directing The Forest and helmed Zeller’s The Height of the Storm in 2018, to describe the 42-year-old, the first adjective he offers is “certain”, before adding: “He has a sort of intellectual certainty about what he wants, or what he feels his work needs.”

Oscar winner or not, Zeller is one of the most courteous people I have interviewed. He apologises for not meeting in person (he experienced life-threatening asthma attacks as a child, which may have contributed to his Covid cautiousness). He pauses to consider each question before crafting careful answers.

The central character in The Forest is a well-to-do man who has had an affair and loses his bearings as his life threatens to unravel. “The subject of the play is anxiety,” Zeller says. “I think it develops in the brain in a circular, obsessional way and creates the illusion of hell. It’s the story of a man who falls apart before us.” Was he writing from experience? A pause. “Yes, I know what it is. And guilt, too.”

Zeller started working on The Forest years ago but didn’t find the structure he was looking for until he picked it up again in 2020, in the wake of France’s first lockdown. The play’s working title was Trains Across the Plains, a lyric from a beloved, enigmatic French song by Alain Bashung, At Night I Lie.

Red herrings abound. “They’re two people who are lying about their feelings,” Kent says of the unfaithful central character and his wife when I visit rehearsals and see Gina McKee and Paul McGann refine one version of a scene that recurs several times with different dialogue. “Just make it more awkward,” Kent advised McKee, who tried different ways to suggest that the wife wasn’t nearly as oblivious as she might initially appear.

Watching them at work, it is obvious how much Zeller conveys in very few words. His lines, translated by his frequent collaborator Christopher Hampton, are concise, often anodyne, yet pointed. (The line “Seemed rather important”, about a phone call, managed to sound at once concerned and passive aggressive.) “When I did The Height of the Storm, [for] the first week or so the actors felt constrained,” Kent says. “Then when they bought into it, they found that if you observe the rigour of it, it gives you total freedom.”

While reality is slippery in many of Zeller’s plays, The Forest takes it a step further. “It’s a strange combination of surrealism and Pinter-like austerity,” Kent says. “He deals in metaphysics, which is not particularly an Anglo-Saxon pursuit.” As in The Father’s screen version, Zeller was inspired by David Lynch: the fragmented nature of the play is meant to reflect the “deep duality” of its central character. “I’ve always been fascinated by people who are capable of maintaining that duality without guilt or anxiety causing it to collapse,” he says. He mentions a former French minister, Jérôme Cahuzac, who denied point blank that he had had a secret offshore bank account before being convicted of fraud and money laundering in 2016.

It could apply to many people in public life these days, I point out. From politics to sexual harassment cases, outright admissions of guilt are now vanishingly rare. “Yes. There is something like madness in the ability to not acknowledge reality,” Zeller says. He quotes from a song by Michel Houellebecq (yes, the French novelist once released an album): “We need to attain a clarified heart.” He adds: “I think we hold ourselves upright in life when we manage that clarified heart, when we know what we want and who we are.”

Zeller appears to have achieved it. He was raised mostly by his mother while his father worked in Germany as an engineer, and he achieved fame early in France with a series of youthful novels, winning the prestigious Interallié prize aged 25. His pivot to the stage came when he was asked to adapt the libretto of a rare opera, Zoltán Kodály’s Háry János, in 2002. The collective nature of theatre appealed to him and he turned out to be inordinately good at it, achieving a rare level of international popularity for a French playwright, with multiple West End and Broadway hits.

He is guarded about his personal life, but in 2010, he married the French actor Marine Delterme (best friend to the former first lady Carla Bruni), who recently called him “the noblest soul I have ever met”. Zeller has a son and a stepson with Delterme. His play The Son, which portrays a teenager’s mental breakdown, was partly inspired by Zeller’s own experience as a father.

Zeller is currently editing the film adaptation of The Son, which he shot mainly in London last year. He has thoughtful praise for all of the cast members, from Jackman – “extraordinary, generous and brave” – to Dern, whose “quality of being” he describes in very French terms. And he added a role for Hopkins, as a difficult grandfather who was merely mentioned in the play. Did he name the character Anthony again, as he did to convince Hopkins to play The Father’s title character? “Yes,” Zeller admits sheepishly. “We experienced something so intense with The Father and what happened next, that I wanted to extend it. I have a lot of tenderness and affection for him.”

The Father’s awards run “made things easier” when it came to financing his second film, he says. “When the Oscars happened, my first thought wasn’t that it would open the door to blockbusters. It was that I would be able to do The Son, despite the difficult subject matter.” I ask jokingly if Marvel films may still be in his future. “No,” he says quickly, before looking worried: “But I’m not judging.”

Zeller has yet to take a holiday since last year’s Oscars. He will soon, he says. “I’m not very good at holidays. What I’m really passionate about is work. Some people have fixed hours to write but I have the opposite problem: I try to schedule moments when I won’t work.”

The mostly virtual 2021 awards campaign means Zeller was at least able to be home. “Of course I would have preferred to travel, but it’s no big deal,” he says. Zeller is very close to his sons. The values he has attempted to model for them, he says, are “kindness, benevolence and respect – but they seem like rather obvious things to me.”

I ask him about his younger son’s interest in film-making. For the first time in our conversation, Zeller looks taken aback. “How do you know that?” he says. Your wife mentioned it in a recent interview, I tell him. Fleetingly, he lets his guard down. “Yes, he has a passion for Lego, and he makes little stop-motion films. He is someone who needs to create parallel worlds, to find a sort of refuge in them.” Might it be a family trait? “We always compensate for things when we create,” Zeller says with a smile, before returning to his own world-making.

• The Forest is at Hampstead theatre, London, 5 February-12 March.