According to DCEU storyboard artist Jay Oliva, an early version of The Flash was supposed to lay “the groundwork for Zoom as the big baddy of the DC Universe.”
Miller was at one point planned to star in a trilogy of Flash movies, which would have ended with Flashpoint. Snyder wanted to use the major comic book event to end and reboot the DCEU, allowing new actors to come in as the most famous DC characters after ten years. Snyder’s planned Justice League 2 and Justice League 3 would have led to Flashpoint.
The director planned to conclude his major Darkseid epic with the universe getting to have several heroes as part of the Justice League, like in the animated Justice League Unlimited.
Justice League 2 and the other Snyderverse movies would also be affected by Zoom behind the scenes, leading to the character being revealed as the Snyderverse’s ultimate villain. With a fan campaign for Snyder’s Justice League 2 to be made, perhaps Snyder’s DC plans can be realized some day, even if in another medium.