Mae, to further expand on Karin's explanation, (x2y3)4 = (xxyyy)(xxyyy)(xxyyy)(xxyyy).
If we put everything in order, we have xxxxxxxxyyyyyyyyyyyy, which we shorthand x8y12.
Like Karin said, ANYTHING to the power of zero equals 1.
When we multiply x8y12 by 1 and y5, the same thing applies if we expand, regroup, and do our shorthand.
When it comes to division, remember that anything over itself equals 1. (x8y17)/(x3z8) = (xxxxxxxxyyyyyyyyyyyyyyyyy)/(xxxzzzzzzzz). x/x then happens 3 times, so they become 1(1)(1), which basically cancels out.
We are left with Karin's answer after we do our shorthand with what's left.