Bring a large pot of salted water to boil.

Heat 2 tablespoons oil in a deep 12-inch heavy skillet over medium-high heat. Add white part of scallions and cook, stirring, until softened, about 2 minutes. Stir in clams, clam juice and white wine. Bring to a boil and cook, covered, until clams open, about 6 minutes. Remove from heat.

While clams are cooking, cook pasta until al dente. Drain pasta and transfer to a large serving bowl. Immediately add clams, juices from pan, remaining 2 tablespoons oil, scallion greens and lemon zest; toss to combine and serve immediately.