What is the easiest way to beat yoob I've beaten it before but it took..

You never actually face Yoob. You just end up in his stomach. If you are talking about that egg monster at the end of that level, you have to attack the eggs he throws. You'll see a Yoshi get out of the egg, and go and start trying to help you fight by pushing something (I forgot what it was). Finish off 5 eggs, and then all the 5 Yoshis will get enough strength to push the thing off the cliff and land on the monster. He'll be weak for a few turns, but he can still attack. You can tell that his weak spot is that glowing thing in his mouth. Attack that with as much power as you can! Once you do that over and over about a few times, he'll be defeated, and you'll exit Yoob out of...you'll find out.