That's the part I don't like about RTS games... Massive armies, 12 production buildings... Etc. Then it just comes down to like a WWII scenario, whoever makes more shit wins, and has nothing to do with casualty rates, which is where I specialize.
Zerg really bones every way you go... If you don't fast expand (90% of Zerg players do) you have enough reserves and a high enough production speed, to annihilate anyone you 1v1 in a rush, and if they fast expand, you will probably just wreck them... Now if you FE, and they don't, and they rush you, Zerg's production speed is so high, that you can counter immediately without even having units when he rushes you... Because this unit called the Queen, can drop larvae in a Hatchery, so instead of 6 Zerglings in 20 seconds, you have more like 12.
The only positive of a ZvP match for me is, one Zealot can tank around 3 Zerglings... And when upgraded, about 6. Problem is Roaches demolish Zealots, and their T2 counter-parts Stalkers.