Of course, in this case one should add the Bremen - Hannover Airport commute, a hotel night in Zurich ( double plus extra bed?) and taxi and/or train from the hotel to Zurich Airport to the costs.
Swiss Railways and Swiss are offering a rail & fly type package to several German destinations from Zurich. Maybe checking that out might be worthwhile. Also, if you change trains at Basel ( also other options ) you can take a comfortable IC straight to Zurich Airport.