Hall effect, electric conductivity and electron mobility in n-ZnSe crystals, annealed in Zn melt at temperatures from 500 to 950°C, are studied in the temperature range from 55 to 500 K. The sharp increase of the shallow donor concentration is accompanied by a decrease of their compensation from K = N_A/N_D = 0.91 to 0.35, and of the activation energy E_D from 28 to 9 meV, as the annealing temperature of n-ZnSe crystals increases above 650°C. At low annealing temperatures, the conductivity of n-ZnSe is determined by shallow non-controlling donors such as Al_Zn, Ga_Zn, In_Zn. The concentration of V_Zn native defects compensating the shallow donors is sharply decreased and the concentration of the V_Se shallow donors determining the conductivity of crystal is sharply increased, as the annealing temperature increases above 800°C. The decrease of annealing temperature of the samples below 650°C results in a drastic decrease of the conductivity of the crystal, a decrease of electron concentration, and abnormally low mobility values. The observed anomalies of transport effects are found to be caused by the presence of a random potential relief in n-ZnSe samples.