https://www.gamespot.com/articles/pokemon-go-zapdos-available-through-new-research-q/1100-6458653/

A new selection of quests are now available in Pokemon Go. Developer Niantic has rolled out another batch of Field Research tasks for the popular mobile game, and completing them could result in another chance to encounter one of the game's first Legendary Pokemon, Zapdos.

Niantic hasn't detailed what the new Field Research quests entail, but they revolve around Flying- and Electric-types and "include skill-based challenges that will test your abilities as a Trainer." As before, players will earn one Stamp each day for completing a Field Research task; if they manage to collect seven Stamps, they'll achieve a Research Breakthrough, the reward for which is another chance to capture the elusive Zapdos.