Dave Portnoy, Josh Richards Unload On Zach Bryan In Diss Track

The Zach Bryan and Brianna LaPaglia split just got a whole lot uglier ... with Dave Portnoy and Josh Richards releasing a ruthless diss track aimed at the country music star.

The song -- titled "The Smallest Man" -- dropped Tuesday night ... with Portnoy and Richards continuing to show support for their "BFF's" podcast cohost following her bombshell split from Bryan.

In the song ... the duo makes reference to the country music star's 2023 arrest, being active on dating apps and accusing the singer of spreading STDs.

When Portnoy was given the floor ... he brought up how Bryan said Kanye West was better than Taylor Swift -- even though ZB later blamed the statement on being drunk.

El Pres also dropped bars about Zach's height, claimed he had a "booze problem," and said he's a Morgan Wallen clone. In all honesty, there are countless jabs throughout the five-minute project ... and the accompanying visuals are just as ruthless.

While Bryan has not publicly commented on the track ... he seemingly teased a breakup song a few weeks ago after announcing his split from LaPaglia -- including a line saying, "Recall when we, went to Rockaway Beach, summer heat in eastern Queens, and a subway ride."