A zebra undoubtedly has a longer digestive tract than the lion itself.
Also just note that is Humans lack the enzyme necessary to digest cellulose, so comparing a herbivore(zebra) and a lion(carnivore) you would need to use the information and determine how they digest their food. So with a lion, his mouth lacks salivary enzymes. Due to the lack of salivary enzymes, food spends little time in the mouth of a carnivore