Z is used for different quantities in different contexts. In this case, I assume we are all talking about the "compressibility" factor, since it looks like we are all talking about PVT properties of fluids.
Two basic approaches that I see for computing compressibility (whether you use Excel or simulator or slide rule):
Take PVT data and plug into the basic "ideal" gas law: PV=ZnRT. Solve for Z.
Choose an appropriate equation of state, and solve that equation for "Z".
I assume that you want to use this latter approach. Since you have not specified which EOS you want to use, I will simply refer you to Wikipedia's EOS page. https://en.wikipedia...uation_of_stateThe basic approach that I see:
1) Choose EOS
2) Collect pure component and mixture data needed by EOS (critical properties, binary interaction parameters, EOS specific parameters, other??).
3) Solve EOS for given mixture composition, T, P to get V and or Z.
Of course, the details of 2 and 3 will depend on the EOS chosen in 1.