Hi, I don’t have the answer for your exact specs, but I can tell you that my DB 32 (non-zipped) can only accommodate a 13” MacBook Air, and the fit is snug. My MacBook can go in horizontally, but only when I remove my bag organizer. With the organizer in, it can only fit vertically with about 2” coming out of the top of the bag. It’s not a major issue for me because I’m only carrying my computer on short trips to and from my apartment/car/workplace. If I relied on public transit or walked farther than short trips to and from parking lots, then I would use a different bag to commute with my laptop.
Based on my limited experience, I would say that you will most likely have trouble getting a DB zipped 32 to work with a 15” laptop.