Have a look at the Functional Attributes command, found on the Analysis ribbon tab of GeoMedia Desktop. First connect to your shapefile within the GeoWorkspace (you can use drag-and-drop if you're on GeoMedia Desktop 2020). Then when you create your functional attribute, you can use an expression like "Z(POINTS(<geometry field name>))" to create an output functional attribute named something like "ZValue". This expression will expand all geometries to their individual vertices, then return the Z value for each vertex as a numeric attribute. Keep in mind how intense that is, if you have a lot of data with a lot of vertices. If you then use the Attribute Query command to filter "where ZValue=0.0" and symbolize the output as big red dots :-) then they should jump out to you in the display pretty well.
Of course you may not be interested in understanding the situation at a vertex level, but rather at a geometry level. In that case, you can expand the above functional attribute as you think suitable to your case - e.g. do you want to know if there is at least one zero value, or only if all vertices on a geometry have a zero value. However you go about it, you can summarize the Z values for an entire geometry pretty easily. For example, to average the values, try "AVERAGE(Z(POINTS(<geometry field name>)))". - Hal
