Things You'll Need
Instructions
Fly to Fallarbor Town and travel east to reach Lanette's house in Pokemon Ruby.
Search the grassy area right outside of Lanette's house until you encounter a Zangoose. Weaken it through attacks until its health is in the red region and inflict Sleep or Paralyze if you can. Throw Ultra Balls at Zangoose until you catch it. It will probably take a few Ultra Balls.
Fly to any Pokemon Center and make sure to have Zangoose in your party. Go up to the second floor and use the middle machine to initiate a trade with another player.
Connect the link cable from your Game Boy Advance's USB port to another Game Boy Advance's USB port. Make sure the other GBA has Pokemon Emerald on.
Trade any Pokemon of your choice from Emerald for Zangoose in Ruby.