We present a new development in our approach to the covariant quantization of superstrings in 10 dimensions which is based on a gauged WZNW model. To incorporate worldsheet diffeomorphisms we need the quartet of ghosts (b zz , c z , β zz , γ z ) for topological gravity. The currents of this combined system form an N = 2 superconformal algebra.The model has vanishing central charge and contains two anticommuting BRST charges,