Zapdos

Great League: 1.5 / 5

Zapdos is a good Pokemon: this statement is an absolute fact. However, it has a serious problem: while its typing and strong moveset allows it to hit very hard and excel as an Electric-type attacker, it's also horribly invalidated by threats such as Steelix, which will basically make it seem as though you left one of your Pokemon out of the fight entirely. In the Great League in particular, this leaves Zapdos in a bad place, which is compounded by the limitations on its CP for the league. The addition of Drill Peck from the July 2019 move rebalance gives Zapdos more versatility, though it isn't enough to offset the poor bulk and exploitable typings. 

Ultra League: 2.5 / 5

Zapdos isn't bad per se in the Ultra League; it unfortunately just doesn't have a real place in the current meta. It does resist Registeel's charged moves, and deals super effective damage to the likes of Togekiss, Lapras and Poliwrath, but it can still struggle at beating them, and has really bad matchups against other major threats such as Giratina and Swampert. Zapdos has its niche use, but there are superior choices.

Master League: 3.5 / 5

Zapdos shines brightest in the Master League, where its high CP leaves it unbound as a top Electric-type pick for the tier. The list of threats that it can eliminate grows in this tier, granting it niches against Lugia, Metagross, and Lucario in particular. However, once again, many other threats see it as a paper doll. Zapdos' Flying-typing also gives it advantages, such as a resistance to the nearly ubiquitous Counter-users, but it also leaves it with weaknesses to moves that many of the Pokemon that it would like to otherwise counter. On top of this, Raikou's access to the narrowly resisted and very powerful Shadow Ball puts it in a stronger general place as an Electric-type for the tier.