Zanka said that Brentford must “reset and get ready for United” following Saturday’s 2-1 defeat to Burnley.
Fellow defender Kristoffer Ajer scored a late goal as the 10-man Bees lost narrowly at Turf Moor.
“The sending off made the game a bit more difficult than we’d hoped,” Zanka admitted.
“Against any team in this league, it would be difficult to play with a man down; having to do that for 90 plus minutes is difficult. I think we did what we could, we created chances, and on a luckier day one more goes in.”
The centre-back added: “There’s always something to take from a game. Right now, we have to lick our wounds because we came here to win and we didn’t. It’s on us to reset and get ready for [Manchester] United. We have to come out flying.
“The fans knew what a mountain it would be, going one man down and one goal down and having to play 90 plus minutes, but they were great and we need that support. It warms all the boys that they were there after the final whistle clapping us off.”