Instructions
Fly to Sandgem Town and enter the small house on the southwest part of town. Talk to the little girl inside to find out which Pokemon are swarming. Talk to her each day until she says Zigzagoon is swarming.
Travel to Route 202 and walk around until you have a random encounter with a Zigzagoon. This should happen within two Pokemon encounters.
Select a Fighting Type Pokemon to weaken Zigzagoon. Do not pick a Ghost Type. Attack the Zigzagoon to wear down its health points without knocking it out completely.
Select a Pokeball from your trainer menu when Zigzagoon's health is low. Use the Pokeball to capture Zigzagoon.