Zach Bryan has had it with the haters since his split from Brianna "Chickenfry" LaPaglia, and he’s not holding back -- it was time to let the trolls have it!

The country singer let loose on IG Thursday, firing back at his critics and calling out the "f***ing weird couch warriors" targeting his friends -- even going as far as to say their behavior was so bizarre, they should be "studied for science."

Zach rebuffed the ridiculous rumors of him juggling 4 different girlfriends in 2 weeks, setting the record straight that he's single and staying that way. He said it's all about his friends right now ... who, according to Zach, are being harassed and receiving death threats online.

Zach says the haters’ actions are so vile, it’s making him question whether he even wants to stay in the public eye trying to keep making good music for his fans.

As TMZ reported earlier, Zach threw fans for a loop back in October when he announced he and the Barstool Sports podcaster had split after more than a year of dating.

In the aftermath, Brianna aired their dirty laundry all over social media and her podcast, accusing Zach of infidelity and emotional abuse. But Zach? He stayed silent -- until now.