start with multiplying z to each. you don't multiply it to the 6 because it is in the same parenthesis set, but you multiply it to everything in the other set. After multiplying, you get: , ,
now do that to the 6. After multiplying you get: , ,
now set it all next to each other + + + + +
now combine like terms. start with the to the highest power. since there is only one that has a third power, you put that one first. then you combine the squared ones, and so forth.