Crab and Herb Fettucine

Boil wine, vinegar, and shallot in a 2 1/2- to 3-quart heavy saucepan over moderate heat until liquid is reduced to about 1 tablespoon, about 3 minutes. Add a few tablespoons butter, whisking constantly. Add remaining butter 1 piece at a time, whisking constantly and adding each new piece before previous one has completely melted, lifting pan from heat occasionally to cool mixture. Reduce heat to low, then add crabmeat and cook, stirring occasionally, until just heated through, about 2 minutes. Remove pan from heat and stir in herbs, zest, lemon juice, and salt. Meanwhile, cook pasta in a 6- to 8-quart pot of boiling salted water until al dente. Reserve 3 tablespoons of pasta-cooking water, then drain pasta. Toss pasta with crab sauce and reserved cooking water in a serving bowl. Season with salt and pepper.