Sources inside the Dillon's Irish Pub in Hollywood tell TMZ ... Zac, Ryan, Rumer Willis and a few other friends ordered a total of 7 Kamikaze shots, 8 or 9 mixed drinks and 3 - 4 beers.
Zac and Rottman both left the bar at around 9:30 and went their separate ways. We shot video of Zac running from the bar to his car, though it appears Rumer drove him away. By 9:45, Rottman was in police custody.
Rottman apparently was hammered. Cops spotted him after he drove up a curb near Dillion's. He blew a .19, more than twice the legal limit.
We asked Zac's rep if the actor urged his friend to take a taxi or find some other way home that would not have put him behind the wheel. We did not get a response.
So we ask ...