What physical characteristic leans heavily toward the donkey parent in a zonkey's presentation?

Answer

The general physical form and mass

The general physical form, mass, and structure of the zonkey predominantly resemble the donkey parent. Quantitative measurements, particularly concerning weight and overall bulk, suggest the donkey dam sets the template for the hybrid's size. While the zebra contributes muscular density and pattern, the resulting creature often looks much like a mule but possesses the distinctive dark markings.

What physical characteristic leans heavily toward the donkey parent in a zonkey's presentation?
animalzebrahybridZonkeyDonkey