Im doing this by memory but i think you delete the red one in the middle on the right side and it should cause a huge chain. Then you have to do a little transfering the outside guys. Sorry thats all I remember. If i had a screen shot I could do better.
I figured it out, first start by deleting the second from the top red demon on the right hand side, it should cause a chain and it will give you 7 moves. then delete one of the red monsters on the left hand side and move the spare purple demon onto the left side. Then you move the grey horse to the middle (to the right of the red demon). Then you just form your red horse.. then move the 2 grey demons on the grey horse.