The Christopher Nolan Batman universe is completely separate from that of Zack Snyder's — which is kind of ironic when you think about how much Snyder loves mashing together previously distinct universes.
This distance was partly why Christian Bale was not re-selected for the part, which the 42-year-old actor was less than happy about, though Snyder has admitted he did consider getting Bale on board — but NOT as the Bat.
In an interview with Australian website Film Ink, published yesterday, Snyder said:
"This is a total and opposite reality from the Chris Nolan movies. It’s another universe, so we couldn’t hire Christian Bale if we wanted to, because he doesn’t exist in our world. Maybe we could hire him to play another part. We did talk about that briefly. I just wanted to hire Christian to play another part to make that obvious. Christian could play, like, Alfred with age makeup. No! Of course not. But you know what I mean."
It's possible Snyder was joking and that Bale was never considered, but it appears he's gesturing towards conversations that were had in pre-production about whether or not to hire Bale.
Obviously he's mucking about when he suggests having Bale as Batman's butler Alfred Pennyworth, but there were definitely some people on the Warner Bros. team who thought Bale might play some part in the new movie. Snyder continued:
"Even people at the studio would say, ‘Who are you getting from the other movies?’ And I was like, ‘Hey, come on guys, let’s all understand, it’s a different world.’ In the Batman universe that Chris Nolan created, Superman would have a hard time existing. That that’s why we did a reboot on the universe, so we could allow these characters to exist together. We needed to do that to have Batman exist in this world."
With audiences already having to come to terms with the new rules of this world, it would have been incredibly confusing to have Bale bobbing around as Lex Luthor or Thomas Wayne.