They don't deny that they wanted this prosecutor fired. What they claim is that this prosecutor is lying when he subsequently claimed to have been investigating Biden's son and Burisma. They say he was actually corrupt, was profiting from such deals himself, and only raised the Burisma/Biden connection after the fact, when he thought it might help him politically.
Now, if Biden or anyone actually states on that tape that they want to get rid of this prosecutor because he was investigating Burisma/Biden, then that's different. But not speaking Russian....
Anyway, if this story is picked up by some more reputable news outlets who report that's what was said, then I'd be more willing to put more stock in it.
They are speaking Ukrainian, not Russian, but the issue is the same. I listened to the phone calls and there is nothing in this that would confirm that Poroshenko was pressured by Biden to fire Shokin because he was investigating Burisma. To the contrary, it sounds like Poroshenko went to Shokin and was told he had not found any evidence of corruption of some loan deal so Poroshenko asked and received his resignation.
Shokin has stated that he had refused to prosecute Dmytri Firkash because he did not have any evidence of corruption and that may have been what became the pretext to fire Shokin. Biden maintains that Shokin was fired for refusing to investigate Burisma but this is not clear from the discussion. Of course, the new prosecutor, Lutsenko, quickly closed all investigations of Burisma so this would conflict with Biden’s explanation that Burisma needed to be prosecuted.
There is nothing here that explicitly shows that Biden or Poroshenko were aware of Shokin’s investigation into Hunter Biden or Burisma. Bottom line, no smoking gun.