I think you've never swung a sword like that before. [The answer's flat and brutally honest, but he's quick to raise a finger to explain.] A zanbato is an anti-cavalry sword by nature. Not a bad choice considering what you're up against, but your technique needs work. Try swinging it vertically more than horizontally. It will require more precision, but you can have gravity work in your favor that way. A horizontal swing can still be effective, but don't treat the weapon like a bat. It's more of a lever. Make it do the work along with you. Wasting too much energy in a swing will make it hard to recover from a strike and leave you open for a counterattack.

[He holds his arms in a position like a proper stance, and makes a couple of practice motions to illustrate what he means.]

Give it a few tries. Don't worry if it feels awkward at first, swordsmanship takes practice. You can do it. Remember those basics when you go in there.