Then you quickly zoom out to 200 mm, BUT you don't choose a correspondingly faster shutter. Just the act of pushing the shutter release causes vibrations, no matter how gently you do it. Use a cable release or the self-timer. Cable releases get lost fairly regularly, so carry a spare. I can pass a driver's license vision test without glasses, but I wouldn't dream of photographing without them.
Many photographers prefer a plain matte screen with grid lines.
Also, don't over focus. Your vision will be most discerning in the first two or three seconds. The f-stops on a lens are not created equal, at least in terms of resolution. Almost always, there are one or two f-stops better than the others. Often, but not always, these are f8 or f1 1.