Terran and Protoss are both equal end game. Zerg has to win before that, or the chances of them beating a 200/200 terran / protoss army is slim
it really depends on the army composition. zerg is capable of winning in lategame with T3 units (brolord/infestor combo). often they just don't tech up and stick to muta/ling/baneling or roaches which get stomped by a "deathball" - mech, colossus/HT/archon and so on.
Hunter seeker missile is terrible, so thats not really a viable option, he would have just fungled the raven as he realized what was going on, the range is far too short