The Lee-Kesler EOS is a three parameter correlation, in addition to Tc and Pc, you'll need the acentric factor for the fluid of interest.
First, determine the ideal reduced volume of the Lee-Kesler "simple fluid" (w = 0) using the Tr and Pr of the fluid of interest. Calculate the simple fluid compressibility (Zsf = PrVr/Tr).
Second, determine the ideal reduced volume of the Lee-Kesler "reference fluid" (n-octane, whose w = 0.3978) using the same Tr and Pr of the fluid of interest. Calculate the reference fluid compressibility (Zrf = PrVr/Tr).
Lastly, find the compressibility of the fluid of interest by interpolation/extrapolation based on the acentric factor of the fluid of interest. [Z = Zsf + (w/0.3978) x (Zrf - Zsf)]
The 3rd Ed. of Sherwood, Reid, and Prausnitz has all the equations and tables you need.
Good luck,
Latexman