Heisenberg didn't build the entire factory from scratch, the labyrinth of the factory tells us that there was a factory there long ago.
Fair, completely forgot about that part. Been a while since I've played 8. Though, that doesn't really mean
that much since the building the factory was probably the least impressive part of his whole scheme.
Also, when you enter the factory gate, you will see that there is a German Panzer in front of the factory. He found them ready somehow and used them to modify his cyborgs.
So he used the metal from the scrapped tanks to make his cyborgs? Yeah, that doesn't make the feat any less intelligent, since none of the internals that allow the zombies to run and such use pieces from them; the only ones that do in any capacity are the aptly named panzers, which he welded the body plating of the tanks onto to support their defense and offense. Every other technology made by Heisenberg is made with scrap metal.
Heisenberg was using corpses with Cadou, and Cadou already had the ability to create zombies on own.
Also fair, thought that he didn't use the Cadou for some reason lol. But after looking into it, it seems like the Cadou didn't even do much of the work, only actually reviving them; Heisenberg was the one that replaced their hearts with the Cadou instead of just normal infection, built a reactor around that to power the body and created technology to electrically stimulate their muscles and simulate brainwaves in them.
Is there any proof that Heisenberg programmed them in such detail?
He has them outfitted with a device that stabilizes their physical movements by simulating brainwaves, allowing them to engage in combat and even be able to understand language and commands to a certain extent, as seen with Sturm. This is the kind of shit fleets of scientists and researchers have been trying to create and develop for decades now due to things like paralysis, Parkinson's, and nerve damage, and we collectively have barely managed to do a fraction of what Heisenberg has done with just rusted junk.
Great! She created something like Cadou and you only mentioned her as helping to research some viruses.
Creating the Cadou is impressive, but Miranda didn't just build them from the ground up in a lab or something; she exposed nematodes to The Mold so that they would have the same DNA altering abilities as it whenever someone was infected by them. And hell, if you really want to talk about failing and faulty creations like you mentioned earlier, the Cadou are scoring like, what, 7? 8 somewhat "successful" infections out of however many infected there are in the game? Because that was the purpose of the Cadou: to create a host body for her daughter. And even then, when she did find a host, it came from, not her Cadous, but from the infection caused by The Mold itself across the planet without her involvement.
As for why I mentioned the viruses, it's because that's a really solid ass feat, and probably qualifies her for Gifted, likely Genius by itself. The ones we see in the game are genetically modified strains that are crazy and far beyond any sort of man-made disease in real life.