He's just a puppet, so he's weaker then the real Ganondorf. Here goes...
BATTLE STEPS:
1. Get him off his horse if you can.
2. Then on the right time, hit that ball of light that Ganon shoots you.
3. He'll also reflect as well so keep on doing this until he's stuned not you...
4. Go near it as possible and swing your sword at him.
5. If you cannot reflect, use your Hyrule Shield, it may save your life but won't help you
beat it...
6. If it tries to charge... RUN!!! You have no chance of reflecting this one! He'll kill
you!
7. Repeat these steps 1,2,3,4... The you should have won.

Well, good luck on that, but if you're confused go ask someone else...