Good fight! BA has the better demonstrated speed feats, so he might have the edge in this matchup. That said, Zod is no slouch in speed either; as a Kryptonian, he possesses a significant degree of superspeed himself.
Zod literally beat two Flashes and Supergirl a nigh-infinite amount of times. Each time, Barry 1 and 2 and then Barry 2 continually learned, to a ever-increasing extent, how to fight Zod, but couldn't cut the mustard. The Flashes also killed Nam-ek and Faora, who are no slouches in fights (well, maybe Nam-ek).
Pre-Flash 2023, Adam takes this for sure, but not anymore. The final fight sequence capabilities from Zod take a giant dump on Black Adam.
So how fast were the Flashes operating in those scenes? If we don't know, we can only estimate their average operating speed. Scaling is only valid when compared to another character's average performance, as characters operate at different levels at different times.
BA also moved relative to propagating lightning and was shown to statue the battlefield in a similar way to how Flash was depicted on multiple occasions.
Make no mistake - the Flashes are faster than both Zod and BA. Zod never actually matched their speed; his durability was the key factor. Plus, the sheer number of Kryptonians on the battlefield played a major role in their repeated losses.