The presence of multiple versions of Batman in The Flash reveals a DCEU problem that James Gunn and Peter Safran's DC Universe will likely avoid. The Flash gives its titular hero his first ever foray into the big screen with a high-stakes story that puts the fate of the multiverse on Barry Allen's shoulders. However, Ezra Miller's Flash shares the spotlight with Supergirl, General Zod, and two Batmen, not to mention a wide variety of DC characters from different universes who make a surprising appearance thanks to the Flash's Speed Force powers.
https://screenrant.com/the-flash-movie-batman-problem-dc-universe-fix/