Once you defeat Zapdos, it is gone from the game and cannot be re-encountered.
Here's why:
* One-time encounters: Legendary Pokemon in FireRed are designed to be one-time encounters. This creates a sense of accomplishment and rarity.
* No re-spawning: While some wild Pokemon respawn after a certain time, Legendary Pokemon do not respawn in FireRed.
* No trading: You cannot obtain a Zapdos through trading in FireRed.
However, there are a few ways to get Zapdos in other ways:
* Trading: You can trade with someone who already caught a Zapdos in a different game.
* Using cheat codes: You could use cheat codes to force Zapdos to appear again, but this is not a legitimate way to play the game.
If you missed catching Zapdos, you'll have to rely on these alternatives.