The Third Beast - The Leopard with Four Heads
As I have done with the other two beasts, the lion with eagle's wings and the bear with the three ribs in his mouth, let's assemble a complete image of the third beast, the leopard with the four heads and the four bird's wings. The first thing to notice is that this beast is the weakest of all the four beasts. The leopard is not as strong an animal as a lion or a bear and certainly weaker than the fourth beast that is "terrible" in appearance. 

The leopard is also weak when you consider it has bird's wings unlike the first beast that had eagle's wings; the bird being a much weaker animal than an eagle. I believe the leopard is also symbolic of the multinational organization, the United Nations, embodied by the ram in Daniel's vision of the ram and the goat. I believe the four bird wings of the leopard are representative of all the countries in the world because the four wings represent the four directions (north, south, east and west). 

This is also shown in the book of Daniel (Daniel 2:39): "And after thee shall arise another kingdom inferior to thee, and another third kingdom of brass, which shall bear rule over all the earth." The leopard, the kingdom of brass, has the unique attribute of "having rule over all the earth". The four heads of the leopard are also consistent with the four horns that arise from the ram after the "notable" horn is broken, the four nations that arise from their respective part of the world to rule the United Nations. The evidence that the leopard and consequently the United Nations are not powerful in and of themselves is that dominion is given to them (Daniel 7:6).

Remember that the leopard is also representative of the third kingdom mentioned in Nebuchadnezzar's vision of a statue, the kingdom of bronze that forms the waist and the legs of the statue. The bronze represents a military power that is an inferior in strength to the iron kingdom that represents the fourth kingdom. 

The bronze that forms the waist and then the legs also represents the idea that the third kingdom will be unified in the beginning but later is will be separated into several parts. This is again consistent with the image of the ram having one horn and then having it broken and replaced by four horns that rise up later.