The e(+)p neutral-current deep inelastic scattering differential cross-sections d sigma/dQ(2), for Q(2) > 400 GeV2, d sigma/dx and d sigma/dy, for Q(2) > 400, 2500 and 10000 GeV2, have been measured with the ZEUS detector at HERA. The data sample of 47.7 pb(-1) was collected at a center-of-mass energy of 300 GeV. The cross-section, d sigma/dQ(2), falls by six orders of magnitude between Q(2) = 400 and 40000 GeV2. The predictions of the Standard Model are in very good agreement with the data. Complementing the observations of time-like Z(0) contributions to fermion-antifermion annihilation! the data provide direct evidence for the presence of Z(0) exchange in the space-like region explored by deep inelastic scattering.