"Well, indeed.  If it was the case that no object was zero, there wouldn't be a number called that.  What does make zero special, among the numbers?"

"Well, indeed.  If it was the case that no object was zero, there wouldn't be a number called that.  What does make zero special, among the numbers?  If you have any ideas here, say them informally first; saying it formally is usually harder, and it's usually wiser to solve the easy problems before you tackle the hard ones."