Honestly that’s a complaint I have about nearly every pencil, not just the zebra. They’re almost always hard and smudgy because the pencil has been sitting out either in a warehouse or on an office supply shelf for like 5 years.
I’d rather bring my own hi-poly brick eraser, or even better, a hi-poly retractable eraser that is a lot easier to control and keep a fresh, smudge-free surface on.