Both SDKs can be installed on the same machine, but they should not be used at the same time.
The two SDKs work with different versions of VisualDSP++.
While Z4 automatically uses the correct version of VisualDSP++, Z3 might start the wrong VisualDSP++ version after Z4 has been used.
Thus please execute “switchtoZ3.exe” after working with Z4 SDK and before starting to work with Z3 SDK.
The switchtoZ3.exe is located in <LabVIEW 2011>\Targets\Schmid\Toolchain\switchtoZ3.exe.