我已经去过动物园三次了

应该是I have been to the zoo for 3 times
因为这句话应该是现在完成时,而不因该是过去完成时
因为这句话不是说我过去去动物园去过三次,而是我现在已经去过三次动物园
表现在的状态

I have been to the zoo for 3 times

如果你要表示你在什么之前的之前就用
I had been to the zoo for 3 times?

I had been to the zoo for 3 times.去动物园已经是过去完成了的事了。我觉得是不是应该是 I had ever been to the zoo for 3 times

用have been to.后面无具体的时间标志，而且是已经发生在过去了的

have 用现在完成时