Zack Snyder effectively created the DC Extended Universe. However, it's no secret that the divisive director's creative decisions haven't always panned out. As the DCEU prepares to move on with its schedule of superhero films for 2022, which includes solo outings featuring The Flash, Black Adam, and Aquaman (not to mention Matt Reeves' The Batman), there've been talks that Warner Bros. is planning to wipe the DCEU's slate clean going forward.
While this would make sense to some extent, especially if Warner Bros. wants to move on from Zack Snyder, it appears that this isn't happening.
Zack Snyder's movies are still canon in the DCEU
Ezra Miller first starred as the Flash in 2016's Batman v Superman: Dawn of Justice. They have since reprised the role in several other DCEU films and TV shows. Now, they are set to star in The Flash, which will premiere on November 4, 2022.
A few days ago, there were reports that The Flash's plot will revolve around deleting Zack Snyder's previous film from the DCEU. This would be a massive undertaking if true. Snyder's movies make up the majority of the DCEU. If this happened, it would result in a soft reboot of the entire cinematic universe. Because of how the move would make sense, many jumped on the bandwagon and believed that this was going to happen.
Fast forward to today and Ezra has confirmed that The Flash will not soft reboot the DCEU.
Ezra Miller responds to rumors that The Flash film will "erase" the Snyderverse. from DCEUleaks
Decanonizing Man of Steel, Batman v. Superman as well as Justice League would give Ben Affleck's Batman and Henry Cavill's Superman an out from the DCEU. This would make little sense as Cavill is a fan favorite and has expressed his interest to don the cape once again. Meanwhile, Affleck will return as Batman in The Flash alongside Michael Keaton, who will play his version of the caped crusader from the 90s classic superhero films.
TLDR; the rumors about DCEU's attempt to "cancel" Zack Snyder's previous movies are false.
With that said, The Flash is still a pretty big deal for the DCEU. The film will explore multiple realities and multiverses. Not to mention, the plot will reportedly set the foundation for future DCEU films. We don't know just how it will do that, but since it's already finished filming and all but set to premiere later this year, we won't have to wait for too long to find out.