I need to upgrade my coyote rifle glass as well. I currently have a 4-16x40 and I think the power range is perfect for how I hunt. It would be useful to have a 50mm objective though for low light conditions.
As for the z-plex reticle, it is great if you are using factory type loads and open areas. Sure you can make it work to your loads, and commit the corresponding holds to memory. I think it is a bit cluttered for use inside a bush though. Too many distractions and options to consider in a short time.