A scarlet funnel cloud erupted in the middle of the exchange floor. Batman didn’t blink—he couldn’t track it. Glass cases shattered in sequence. Diamonds lifted as if carried by an invisible hand. Then, just as fast, the blur resolved into a young man in a tight crimson suit, a golden lightning bolt across his chest. He held a velvet sack bulging with gems.

: The series finale, where he joins the full Justice League to defend Earth against the alien invasion force known as The Joining "The Joining, Part 2"

In their team-ups, particularly against villains like the Mirror Master (voiced by John Larroquette), the show highlighted that speed isn't everything. Batman’s ability to predict enemy movements and use the environment often proved just as vital as Barry’s ability to run at Mach speeds. This mutual respect formed the backbone of their partnership in the show's version of the Justice League. Visual Flair and Animation

I think there may be a bit of confusion here. There is no Batman movie released in 2004 that features the Flash. The Batman films released around that time are: