Generally when adding two zeros together you get 0 (e.g. 1+0+0 = 4). Thats simple.
Multiplying is a litle bit more complcated because,
0x0 = 0, agreed?
yet x^0 = 1.
This is because we generally say that the product of no numbers is one - thats kind of a stock phrase. This means that if you multiply no numbers together you get 1. The same thing happens if you do 0!. You can get the answer by putting 0 into rules for either factorials or indices. Of course this is dangerously close to a proof by definition, I'm not sure there is a much better proof than by using the definitions and seeing what happens if you put a 0 in.
In some ways its more interesting in words. zero times zero is zero, as you are multiplying together two numbers, both of thm zero. But you can write this with zero because you multiply no times at all, if you follow, that is the subtle difference. The former of multiplying by zero gives 0. The later, not multiplying anything at all gives one.