The Yoshi in the 1P Mode is extremely easy and hardly worth a fight.
Now the level 9 Yoshi in VS Mode, that's a different story.
Yoshi, as you will see, likes to jump a lot. And as you may know, Yoshi in his second jump will not be fazed by any attack.
During your fight, Yoshi will try to swallow you into an egg.
It's hard roll behind him, but it's easy to just jump when he does it.
When you're above him at any time, he will do an Egg Throw.
First, jump up to the second floating platform; next, jump up all the way to the plafrom with the target and hit that target.
From the platform, fall down along the wall; as soon as you pass the wall, jump up and hit the target with an Egg Throw.
Then come down next the other target and hit it.
Now jump twice and do an Egg Egg to get the target.
After you land on the platform, jump again and hit the next target with an Egg Throw.
After landing on the platform, do (yet again) another soft Egg Throw (just barely tap ) to hit the target.
Now first, jump on the platform that the where the 6th target was located; then get on the moving platform; finally, fall off, jump and do another Egg Throw.
Jump on the little platform on your right, then jump up and land on the platform in the middle of the pit. Then jump up and hit the fourth platform.
Go back to the platform in the middle of the pit and jump on the next platform.
Jump down to your right and fall on the next platform.
Now jump twice to your left and then perform your Super Spin Attack to get to the next platform.
Jump down to your left, then jump up to the next platform.
Jump up some more to get to the next platform.
Go back to platform number 8. Now, you have to get your timing right for this one. Jump down once, then jump to the right and finally use your Super Spin Attack to reach the final target.