Madagascar Kartz

Method 1:
It's important that you do a singleplayer race on this track, as you have to use a power-up to get this achievement. But it doesn't matter, if you're 1st place at the end.
There is only one jump on "Plane Wreck" at the very end. Try to get power-ups and as soon as you have the rocket power up, that makes you faster, save it. When you see the jump, use it. Don't forget to push (jump) right before the jump, like that you will be in the air a little bit longer. The power up should be in use throughout the whole jump. And use 3 different directions! (For example: ) Because if you do the same direction (same trick) consecutively, there will be a little pause between stunts. Shouldn't be a big problem.
Achievement unlocked!

Method 2:
watch video. All credit for the video goes to HachiRokuCH on Youtube!

When taking off for the jump, hit the left side of the track, there is a small rise there. It will give you extra air. It should give you enough air time to perform the 3 stunts without boost and without the rocket powerup.

At the end of the track (jump to finish) hit the boost arrows and jump abit early not at the very end and then hit 3 different stunt combos midair. I used left-up-right, it is just barely possible.