I am super exhausted,” yawns S. Craig Zahler. It’s no surprise. Screenwriter, director, novelist, musician…this American-born artist is one unstoppable creative force. In the two years between Bone Tomahawk, his cannibal western debut, and his second movie, 2017’s prison yarn Brawl in Cell Block 99, he wrote four scripts, a novel and an album. One of them turned into his about-to-be-released third film, Dragged Across Concrete. This man just doesn’t stop.

While nobody can fault 46 year-old Zahler’s work ethic, the content of his movies has concerned some commentators. Playing with genre material, he’s not afraid of provocation. Amid all the critical acclaim, the perceived right-wing politics of Tomahawk and Brawl gained Zahler a reputation as a Hollywood conservative, like Kurt Russell and Vince Vaughn, his respective stars. “On the spectrum, I would be just right of centre,” he later confessed.

Now there’s Dragged Across Concrete. A three-hour crime saga, it stars Vaughn and Mel Gibson as two cops suspended for excessive force who embark on a heist, setting out to hijack the spoils of a bank robbery from a violent gang. “I wanted to do a big scale crime piece and something that’s a little bit more in the style of my novels,” says Zahler, whose penchant for pulp fiction has seen him pen books like 2014’s Mean Business on North Ganson Street.

It immediately rubbed some critics raw. After its Venice Film Festival premiere, the headline for the Daily Beast’s review described it as a “vile, racist, right-wing fantasy”. In the opening scene, Gibson’s veteran cop Brett Ridgeman and Vaughn’s Anthony Lurasetti are seen busting a Hispanic suspect and terrorising his Latino girlfriend — mocking her accent while she’s naked in the shower. Another character later likens being branded a racist these days to being accused of Communism back in the 1950s.

With Ridgeman’s daughter also attacked on the streets by African-American thugs, Zahler wanted to explore just how a character like him might hold such values. “Is this who he innately is or is this who the job has made him or is it a combination? Those are the sort of questions that I’d like to put out there and let people sit with. But it certainly doesn’t come from a place of wanting to condemn police officers, nor say that these are flawless people who don’t make mistakes.”

He says he knows people who work in law enforcement and hospital emergency rooms, and drew from their experiences. “You’re exposed to intensely violent situations and danger and there’s a certain point where all of the people that you’re dealing with are the civilians and they are the ‘other’.” It’s a chance to look at the emotional toll years on the beat brings. “It’s not glamourising or condemning because I’m not making this movie to make a political point.”

Nevertheless, Zahler’s persistent pushing of hot-button topics —police brutality, racial profiling – is made all the more awkward with the casting of Gibson. The actor may be on a comeback after his Oscar-nominated war movie Hacksaw Ridge (which featured Vaughn) but his antisemitic comments (“the Jews are responsible for all the wars in the world”) spouted amid a DUI arrest in Malibu in July 2006 have never been forgotten.

Zahler, who was raised in Florida by a Jewish family and who describes himself as a “Jew-turned-atheist”, was all too aware that defending Gibson’s casting was always going to come with the territory. “He’s a terrific performer,” he shrugs. “I think you see by the wear on his face that is this someone who really has access to a lot of emotions.” It’s exactly what he wanted for Ridgeman. “Just how over it this guy is and how jaded and desensitised he is by the job.”

When it comes to Gibson’s past, Zahler says: “I don’t look forward to being in a position where people are either going to want me to defend him or condemn him.” He seems to separate out art from the creator, citing the time when he used to write for music magazine Metal Maniacs. He once singled out the band Deströyer 666 for praise (he believes their Phoenix Rising is one of the all-time great metal albums), despite the band’s controversial anti-social opinions.

Zahler has his own metal band Realmbuilder (he sings, writes lyrics, drums), which has three albums out on Swedish label, I Hate. Music evolved for him alongside his film career, after he won a place at NYU Film School, where he studied cinematography and animation.

When he graduated, he got a job as a catering chef, but his focus switched to writing.

He started out with a fantasy book. “I worked on this book for 500 days consecutively. There was four days off when I went canoeing in the middle.”

It never got published, but his subsequent novels all have been. His latest, Hug Chickenpenny: The Panegyric of an Anomalous Child, is currently being developed by the Jim Henson Company — the team behind The Muppets. “A gothic orphan tale” about a child born with mutations, including a stump for his left arm, it led horror maestro Clive Barker to proclaim that Zahler is “certain to become one of the great imaginers of our time”.

Then there is the comedy-horror Puppet Master: The Littlest Reich — also in cinemas this week — which Zahler scripted but didn’t direct. The latest in a long-running franchise, and typical of Zahler’s love of old school horror, the puppets in question are brought to life by ancient magic, are the product of a Nazi toymaker (played by Zahler favourite Udo Kier). At one point, a Nazi puppet is tossed in an oven to the line, “I can think of six million reasons why.”

If Zahler is a provocateur along the lines of Danish director Lars von Trier, his one-man conveyor belt of scripts, novels and songs are enough to single him out as a unique voice.

Like him or loathe him, he’s certainly not going to be cowed by political correctness or commercial imperatives.

“I write stuff for myself,” he says. “Past that, I want people to enjoy it, but I’m not making choices so that more people enjoy it.”

Dragged Across Concrete and Puppet Master: The Littlest Reich open on April 19