This is just my opinion but:
There are plenty of reasons for Jimmy to trash Howard's car; the HHM partner constantly belittled Jimmy, stood in the way of his legal career and drove a wedge between the two McGill brothers. However, the reason behind Jimmy's act of ten-pin vandalism goes beyond just the resurgence of an old grudge; like most things in Better Call Saul's recent seasons, Chuck's death is the root cause. Crippled by the guilt and grief surrounding the loss of his brother, Jimmy found solace in becoming Saul - a character that helped Jimmy avoid processing Chuck's suicide. Deep down, of course, Jimmy knows that Saul is a mask, and his brother's death still burns fiercely upon his soul, and this is why he now hates Howard even more - because the successful, perma-tanned "swell guy" has done what Jimmy couldn't.
In season 4's "Breathe," Howard deliberately has Jimmy sidelined from Chuck's will, but is clearly very affected by the entire situation, reacting with an uncharacteristic vulnerability when Kim gives him a dressing down. Later, in "Quite A Ride," Jimmy meets Howard in a court bathroom, and the former king of HHM has fallen considerably, along with the company's fortunes. Howard is riddled with insomnia, seeing a therapist, and no longer representing the most lucrative clients. Although Jimmy shows concern, it's clear when he rips up the therapist's contact card that he feels he has "won" in a twisted sense. Chuck's death broke Howard, but Jimmy soldiered on with a plastered-on grin and a "s'all good, man." He finally got one over on the great Howard Hamlin.
Of course, while Jimmy might've seemed to be handling the loss better than Howard in Better Call Saul season 4, the roles are flipped in season 5's latest offering. Over the course of their lunch, it's made apparent that while Jimmy is still hiding behind Saul, Howard has made it through the other side of the tunnel. By addressing his grief and seeking help, Howard has recovered as a professional, is back to his usual smarmy self, and now has a drive to be more righteous - offering a job to Jimmy, championing his scholarship pick, hugging him goodbye. All of this new-and-improved Howard is summed up by his pretentious "NAMAST3" plate.
And this is why Jimmy makes such a concerted effort to decimate Howard's car. As Saul Goodman, Jimmy is now financially successful and enjoying the kind of morally ambiguous schemes he always reveled in. But Jimmy is far from over his brother's death, with that pain still bubbling underneath unchecked. Howard's recovery enrages Jimmy far more than professional success or snide comments ever could.