Great video and I've now subscribed to that channel, thanks!
It seems to me that although a Zweihander could be used to parry, it should join my earlier suggestion about the pole-arms - that is, it should only be possible to effectively parry with it with sufficient training. Not sure how best to implement that, I mean a Zweihander talent would be the obvious candidate, but I'm not sure that's the best solution.
Another thought I had was to provide a Melee skill requirement for each weapon. If a PC has at least that level of skill, they can use all of the weapon features, otherwise they can only use it with the standard damage values. For Parrying, those weapons would be treated as if they did not have the Parrying feature until the PC has actually learned how to use the weapon properly.
Thoughts?
I make YZE games (https://drivethrurpg.com/browse.php?author=Matt%20Kay) and produce predominately Free League content on my YouTube channel (https://youtube.com/@3skulls)