Zapdos actually could replace both your Pokémon. It can learn moves such as Thunder, Fly etc. I'll provide an ingame moveset, but because this is Gen 1 it won't be very complicated
- Fly (For HM use and good damage)
- Thunder (For very good damage and STAB)
- Substitute (For stalling)
- Thunder Wave (To infect paralysis on some annoying Pokés)
It also has high Speed and Special Attack, and is incredibly powerful.
Hope I helped!