The short answer is "it depends." It takes a lot of energy for a lioness to hunt a zebra - zebras are big and fast, and hunting them is a difficult task. But the payoff can be worth it - zebras provide a lot of meat, which is a valuable source of energy and nutrition for the lioness and her pride. So the answer really depends on the cost-benefit analysis - is the energy expended worth the nutritional payoff? It's also important to consider other factors, like the availability of other prey and the size of the pride.