Notes from author
Most armors and shields are not very good against magic damage. Taking advantage of the large amount of magic damage on the Zwei, you ignore the best armor's best defenses and go for their weakest points. Of course, you have to deal with split damage; you do this by forgetting the fact that your weapon is physical and focus entirely on the magic damage. There are other weapons you can use for similarly effective results, like the Large/Great clubs, but I personally prefer the Zwei over those for its dead-angling ability and being of lesser stat investment.
You have a free ring slot to pick what you like. I do not rely on/know how to optimally utilize spells, so I use Steel Protection over Bellowing. You could forget spells, go Bandit and put more stats into Vitality or something. Grass Crest is interchangeable with other shields that are 3 or below.
Happy hunting.