The temperature dependence of the electronic contribution kappa(e) to the thermal conductivity of a two-dimensional superconductor with Van Hove singularities (VHSs) in the density of states is calculated. The influence of the position of these VHSs from the Fermi level is investigated. Various experimental results on the thermal conductivity of YBa2(Cu1-xZnx)(3)O7-delta compounds with 0 less than or equal to x less than or equal to 0.017 and 0 less than or equal to delta less than or equal to 0.3 are analysed using the above model. A simple relation between x and delta can be extracted from this analysis. This relation is shown to be correlated with the variation of the Cu(2) valence with oxygen content and Zn doping.