Strong and unpredictable early game, solid middle game, strongest late game. It also has some of the best units in the game: zerglings, mutalisks, defilers. Especially defilers, they are arguably the strongest spellcasters in the game

Production speed scaling due to hatches.

If you want 6 carriers at the same time, build 6 starports.

If you want 6 ultralisks or 6 mutas at the same time, build 2 hatches (which you already have)

One consequence of this is that changing army composition as Z is very easy.

Defilers

This is not a viable strategy in competitive play. It's a huge resource/time investment with a dubious payoff.

If you could win as Protoss by building Dark Archons, raiding your Zerg opponent's base to capture a worker, building a bunch of Zerg production and tech buildings, and attacking with a combined army... you most likely outclass your opponent, and could have won much faster using a more conventional strategy.