Callan Mulvey and Zachary Levi come to mind. Mulvey was one of the Hydra soldiers in Winter Soldier and Luthor's Russian henchman (KGBeast, really) in BvS, while Levi was Fandral in the second and third Thor movies, before getting the lead in Shazam!.Seeing David Dastmalchian and Michael Rooker in video and panel for The Suicide Squad got me wondering how many actors have done both the MCU and the DCEU. I know there have been a few others, but I'm drawing a blank beyond those two.
For those unaware or who have maybe forgotten, Michael Rooker was Yondu in the Guardians of the Galaxy movies, and Dastmalchian was Kurt in the Ant-Man.