Demesnedenoir
Myth Weaver
From my limited knowledge, I think Zweihanders that push 10lbs and up were mostly ceremonial and typically weighed more in the 4 to 6 pound area. At some point, it basically became a polearm. I've also wanted to look into the books on halberd dueling but never quite got there.
This. My greatsword is maybe 4 lbs. A ten-pound sword would be one of the big Zweihanders, and it would be six feet long with a 3" wide blade. Even then, it might not reach ten pounds.