As long as the chewing movements and the relationship of two jawbones with each other are correctly determined, no breakage would be expected in daily use. The fracture resistance of zirconia is higher than teeth. However a severe trauma, accidental strong impact might cause the tooth to break.
The chemical properties of the adhesives that we call “cements” used in the bonding of zirconia veneers have ideal properties for staying in place. The methods to increase the retention are also used during the preparation of the teeth, and it is a rare situation that crowns come off.