Unfortenately there's a great risk to destroy the phone without case or screen protector. The fact is, XZP won't survive if dropped hard surface without protection.
My old Z3+ survived because protectors. I drop it about 1m height to concrete floor in display panel first, when i take my wallet from the pocket. Screen protector glass destroyed and Devil Case aluminium bumper takes deep scratches, but phone stay completely intact and functioning. So the protectors may not look nice, but they do their job. And there are exist good looking bumpers and cases, for example Devil Case.
