I'd imagine they'd eat at least twice what an elephant does. Now where are you going to get all that hay? In this economy and weather systems? The only zoos that could support a woolly mammoth would have to be incredibly well funded and I'm pretty sure they don't grow enough roughage in South Korea to afford to buy up enough to keep a woolly mammoth healthy.

Not all zoos are well-funded government-funded institutions. Some are poorly funded by their city/state and some are privately funded and thus far more subjected to the whims of the agricultural industry.

Additionally, who the hell is going to formulate diets for these woolly mammoths? We can only guess what they eat and any zoo vet/nutritionist/keeper can tell you, our guesses are frequently not enough! For example, Bears are fed an omnivore diet that one would THINK supports them fine...but there's an abnormally high rate of biliary cancer in bears. We don't know it for a fact, but the diet is high on the suspect list (although we don't know why).