Really dude
I have on many occasions, sliced through (already dead) 200+ pound boars/wild pigs from hunts/pest control, decapitating them with a single swing with so little effort, its just a matter of getting adjusted and a lil technique. Most functional katanas weigh in at between 2 1/2 and 3 pounds, they are not fly weight swords. The gladius was typically 1 1/2 pounds, the heaviest I have ever heard was 2 1/4 pounds, they are also very poor at slicing through large chunks of meat, they have no curve. Scimitars weigh in approx 2 pounds as well, they are better at slicing than a gladius no doubt.
Some of the boars were well over 300 pounds and make me look small when next to them, and I am not a small guy. Do I advocate using a katana for a zombie, if zombies were to actually exist? No. But unless the day arrives where zombies roam the earth, everything we consider effective is hypothetical at best. I would rather not be so close to a disease/infection riddled body anyway tho