I'm a zerg player,

i dont think there are any easiest race or hardest race.

if zerg is easiest due to mass lings ownage, terran could be easiest as well to have mass marines that own everything XD

or maybe toss could mass stalkers/zealots that easily own lings and etc.

therefore, Zerg is more of a reactionary type of race, where scouting is crucial and the main objective. imagine if you are a zerg with loads of roaches, then 6 Voidrays would easily own all your roaches

just my 2 cent tho