Former Manchester United striker Ibrahimovic converted two spot-kicks – including a Panenka – as the Galaxy defeated the Timbers 2-1 on Sunday.
Ibrahimovic had not played since the club's opening match of the season on March 2 due to an Achilles injury, but the 37-year-old made a goalscoring return in Los Angeles.
After almost opening the scoring with a stunning standing overhead kick, Ibrahimovic netted a 33rd-minute penalty having been fouled by Claude Dielna.
The Timbers – searching for their first win of the season – equalised a minute before half-time via Jeremy Ebobisse.
However, Ibrahimovic ensured the Galaxy made it three wins from four matches with a Panenka spot-kick past Timbers goalkeeper Jeff Attinella in the 65th minute.
Rooney, meanwhile, scored a sensational free-kick in DC United's 2-1 victory away to Orlando City.
After teeing up Steve Birnbaum's header with a whipping free-kick in the sixth minute, ex-United and England captain Rooney produced a moment of magic.
From an acute angle, Rooney curled a set-piece into the far top corner of the net against Nani's Orlando on the half-hour mark.
Orlando forward Dom Dwyer pulled a goal back in the 63rd minute but DC held on to snap their winless road streak – dating back to May 19 last year.