The Karma default flight recording mode is 120k "Linear" POV. My understanding is that the "zoom" function is basically a custom adjustment in-between wide and linear modes, so linear is about as much "zoom" as you are going to get. Your camera doesn't actually have an optical zoom, it is simply cropping the 4K picture giving the appearance of "zoom", but with less resolution.
Some folks will record at 4K or 2.5K and then create zoom in post production as needed. This can help maximize video fidelity. When you can safely do it, moving the drone closer and farther from the object you are filming is also a good way to maximize video fidelity, and is often easier to do with a drone than it is with a handheld camera.