Jake Paul went in hard on Zayn Malik Saturday night, calling him a d***head, adding he deserves everything that's coming to him.
Jake was in Vegas, and as he strolled through a hotel lobby he said of Zayn, "He's a f***ing lunatic. The guy's a complete asshole."
TMZ broke the story ... Zayn pled no contest to 4 counts of criminal harassment after he allegedly got into a screaming match with Yolanda Hadid and Gigi. Yolanda says Zayn pushed her into a dresser. He denies it.
Jake and Zayn have long-standing beef .