A boxing ring is flat – level from one side to another. So why does it always seem like William Zepeda is rolling downhill over his helpless opponents?

Maxi Hughes was just such an opponent, unable to provide resistance in the face of Zepeda’s pressure atop a DAZN card Saturday night from The Cosmopolitan in Las Vegas. At the end of four increasingly lopsided rounds, and seeing their man on the wrong side of this apparently tilted canvas, Hughes’ corner pulled the plug, prompting referee Robert Hoyle to wave his arms and raise Zepeda’s.

Improving to 30-0 (26 KOs) with this win in a so-called “final eliminator,” Mexico’s Zepeda is now the mandatory to two lightweight belts – one held by Gervonta “Tank” Davis and one to be claimed by the winner of the May 11 Vasyl Lomachenko-George Kambosos fight.

After the win over Hughes, Zepeda and his promoter, Oscar De La Hoya, called out those fighters, as well as Shakur Stevenson.

“I next champion in Mexico,” Zepeda, 27, declared in broken English, after conducting most of his postfight interview in Spanish with a translator. “I am ready for Shakur, Gervonta. Whoever is on that list, we’re going after. Now who has to do their homework is Oscar De La Hoya.”

“We believe in William,” De La Hoya chimed in. “He’s ready for anybody. … Shakur, if you’re watching, let’s get it on, let’s go.”

Of course, the likes of Davis, Stevenson or Lomachenko would present a much more difficult challenge than did Hughes (26-7-2, 5 KOs), a serviceable, skilled contender – but one who has lost most of the step-up fights throughout his career.

In a battle of southpaws, Hughes, 34, began well, jabbing with Zepeda, circling with class throughout the first round, exhibiting craft and a game plan as he nearly kept pace with the man broadcaster Todd Grisham described as “the most impressive output fighter in all of boxing.” Still, Zepeda probably edged that opening round, and it rapidly got more one-sided after that.

Given Hughes’ low knockout percentage, Zepeda was unconcerned over the leather coming at him and was able to plow forward relentlessly. He stepped up his body work in Round 2 and seemed to hurt Hughes downstairs. By the middle of the round, Hughes was starting to lose his technique.

The Englishman came out in the third attempting to time and counter Zepeda, but once “Camaron” started ripping right hands to the body, Hughes was in survival mode. In Round 4, his left eye was closing and he was barely able to punch back. Zepeda’s arms wouldn’t stop churning, and he appeared to hurt Hughes with a right uppercut.

Hughes’ corner, knowing Zepeda could keep that pace going all night, showed immediate mercy once their charge slumped onto his stool.

According to CompuBox, Zepeda landed 161 of 408 punches, an average of 102 thrown and 40 landed per round. Hughes’ offense wasn’t bad – he went 53 for 221 – but defense-wise, he had no answers.

Of course, it certainly didn’t help Hughes’ cause that, two weeks before the fight, he ran into visa issues, subsequent travel nightmares and a week’s delay of his arrival in Vegas.

Zepeda’s win compares extremely favorably with how Kambosos did against Hughes last July, when the former lineal champ from Australia eked out a 12-round majority decision. Hopefully fight fans will learn soon how Zepeda compares with the lightweight division’s elite, as the all-action rising attraction has undoubtedly earned an opportunity to test himself against one of the 135-pound class’ established stars.