This time you will be fighting in the air. Vah Medoh is a gigantic, bird-shaped machine and in order to enter it, you have to disable defense mechanisms first. Get ready to fight by wearing an armor that protects from low temperatures, or by eating the right foods. When you're ready, talk to Teba to begin the duel.
You will soar high into the air, above Vah Medoh. The task is to use the glider and destroy the cannons with your bow. In the meantime, Teba will be distracting the enemy, focusing all laser attacks on himself. The task isn't terribly difficult; glide over the chosen cannon and when you're right above it, lower yourself a bit and fire away. After destroying the cannons, you'll be able to embark the machine.