Earlier quoted context omitted.
I think you are underestimating the difficulty of the problem. The interactions between all the stats you listed can’t be distilled to to a single number. For example maybe a very slow but powerful unit gets a normal score, but when paired with fast units to protect it from getting kited becomes unstoppable. A contrived example obviously, but you really do have to see how the units interact with all other units, and…
Interesting. So the Zergling is a weak individual unit but when amassed into a large group they become overwhelming and the overall effect is that the Zerg rush is emergent behavior.
Also their speed upgrade gives them mobility to counter attack exposed buildings. Also their half supply means that they can be worked into compositions when close to the supply cap. Also their fast and parallel time to make means they can reinforce fast after a long battle. Also their general upgrades and late game attack speed upgrade means they can take down buildings fast if there is nothing around to do damage to them. Also if they are spread out they can draw splash damage from power but slow firing units like siege tanks. They can also be sacrificed to burrow and delay an enemy base, used to scout cheaply ...
All that is just from the first attack unit in the game.