Lewis's jab and grab wouldn't work on Ortiz. He can't come out all guns blazing either as Ortiz was a good technical counter puncher. I envisage a good back and forth close encounter similar to the Mercer fight.
You could make an argument Lennox Lewis was the best heavyweight who ever lived. You may not win that argument every day, but there's an argument to be made. Either way, he's right up there ... about as high as anyone has ever gotten. (Stopped a future HOF World Heavyweight Champ to win the Olympic gold in his last amateur fight. Beat everyone he faced as a pro. Retired as champ stopping the next lineal HOF World Champ. Retired with millions.) Any fighter would gladly take Lennox's career over their own in a minute. Luis Ortiz certainly would take it. With both at their best, Luis Ortiz isn't beating him.
Lewis by KO 9 times out of 10. I say that because I'm not sure Rahman(who LL also beats 9/10 x) is any better than Ortiz
Lewis KO under 4 rounds. There would be a feeling out process but the first big right hand Lewis lands on Ortiz's glass jaw would be all she wrote.