The R&S ZVx has different offset methods to shift the calibration plane. These methods are applied after the error coefficients are applied. As such, performing a calibration from ICE, the error coefficients uploaded into ICE, will not be impacted by setting one of these offset methods to attempt to shift the calibration plane.
In the ICE software, there are 2 ways to do deembedding. Both require the Sparameters of the structure to deembed. These can be created with a design tool or using network analyzer techniques.
The first method is to load for a 2 port DUT a 4-port deembedding file (s4p). The use of a 4-port for deembedding allows leakage to ground. Of course, one can convert a 2-port input deembedding block and a 2-port output deembedding block into a 4-port deembedding block. There is a tool provided in ICE to do so (see under ICE Quickstarter: Tools/"Embedding and Deembedding").
The second method is to modify the wiring of the schematic/setup in ICE by introducinga 2-port deembedding block between the DUT and the analyzer.
More info can be found on http://www.nmdg.be/icedoc/deembedding.html (http://www.nmdg.be/icedoc/webframe.html)