Hey Najela, I think you’re closer with this pitch than you were with your last one, but I worry that you’re trying to do too much at once. This feels like two separate stories crammed together–a 20’s mafia heist/chase story, and a supernatural powers/zombie story–and even those two plotlines are made up of a lot of very different elements, some of which conflict with each other. Do you have a plan for how all these elements are going to connect to each other without feeling scattered and random? I can hypothetically see this story working, but it would take EXTREMELY deft storytelling to get all the background worldbuilding out, and strong unifying threads tying everything together. Remember, right now we’re looking for a story that’s fairly short and self-contained, which makes this an even harder sell for this particular round of submissions.
My suggestion is to simplify this as much as you possibly can. Think about your story, and decide what’s the most compelling part of it–the strongest idea or relationship–and cut everything except that concept and any necessary story elements that strengthen and feed into that concept. For example, if you thought the strongest part of this story was the relationship between the reformed criminals and the detectives chasing them, you could cut the supernatural aspect entirely and come up with a mundane way for Iona to reform herself, and focus entirely on the chase and the antagonistic cops and robbers relationship. If you think the supernatural aspect creates the best plot, you could either cut the detectives or have them team up with the criminals early on to deal with the zombie menace–if Iona’s powers caused the zombie problem, finding a way for her to fix it sounds like a goal that would make sense.
A storytelling trick that might help you zero in on your story–you should be able to describe your plot in one sentence. Right now, from the description you gave I can’t even really tell what the main conflict is. I think there’s something in here that could work, but focusing and refining your ideas will give you a much better shot.