The richer you are, the less money seems to be enough.
Having made a clean forty million, Suming originally thought that for the next year or two, he wouldn't need to worry about money. But when he lay down and took the time to think quietly, he found that there were indeed quite a few places where money was needed!
The situation with the zoo wasn't too bad; there was no need for him to put in more money for the time being. The profits from a few projects were enough to cover the zoo's expenses and expansion. Moreover, Suming was the manager of the zoo, not the owner, so there was no reason for him to personally dig into his pockets.
What needed money were the other few private projects of his, each like a hungry child waiting to be fed.