Humans aren't good at running fast, but we are good at running for a long time for long distances, so it's thought that we would just run after things until they got tired.
So like you know how people in horror movies would run and then look over their shoulder and Jason is somehow still there?
Zombies aren't scary. They're popular movie monsters because, while looking vaguely human, they're sufficiently "othered" that you can kill them without remorse (thus acting as a convenient stand-in for other groups that the audience wishes they could do that to) and because they represent an apocalypse that kills most of the people but leaves the stuff behind, meaning that you don't have to deal with society anymore but you'll still easily have a roof over your head and food on your table (albeit mostly canned food.)
That's pretty cool. However, no human has ever won by more than 15min, and every horse has a 15min delay built into their times. So even the biggest winning margin of nearly 11 minutes would have lost to the horse if they had started at the same time.
For it to be scientifically accurate of a comparison, the ratio of weight:human needs to be equal to that of rider:horse, not a direct flip.
In case my phrasing is confusing, to illustrate what I mean here is an example: a 200lb horse carrying a 100lb human is equivalent to a 100lb human carrying a 50lb weight.
The Western States trail in the California Sierras used to be where a 100-mile horse race took place that horse and rider had to complete in 24 hours. At some point in the 1970s one of the riders decided not to take a horse, and he finished in 23 hours on foot. Now it's an annual footrace that the winner finishes in about 14 hours.
This study analyzes historical results of three different man versus horse races (in Wales, in Virginia, and in California). The data shows that human performance decreases with temperature, but less so than horses, so that 30°C is approximately where the best humans can start outperforming the best horses that year.
I would think that even with 15 minutes of intermittent pauses/checks, that time is still productive for cooling the animal and would add less than 15 minutes to the theoretical total if they were allowed to run the whole time.
We can run and breathe entirely separately. Most quadrupeds lack the ability to run and take breaths independently of the pace of each step. Watching cheetahs sprint, for example, show that they have no choice but to exhale every time their legs come together and inhale every time their legs push apart.
Running on our hind legs only frees up our hands to be able to use tools and weapons, maybe even water containers for drinking on the go.
We can see further by standing up, and can make tactical decisions based on terrain, while still running pretty much full speed.
Combined with our unusual ability to cool ourselves by sweating, this gives us an advantage over pretty much any animal in the heat. Wolves and horses can still outrun humans in the cold, but lack the cooling mechanisms to maintain pace in the same heat that we can.
We also have by far the best throwing game in the world. Some animals can spit with reasonable accuracy, some apes can kind of lob shit in a general direction, and there's that one lizard that can spray blood from its eye, but nothing in the animal kingdom past or present has a human's innate ability for ranged attack. The average man can throw a fist sized rock hard and accurate enough to crack a skull from 20 yards with his bare hand. And we've spent the last 10,000 years inventing newer and more impressive ways of throwing stuff.