Lighting is relative.
If you successfully reproduce a shadowbox still life, using Z amount of light in the shadow box and Y amount of light in your studio (assuming here most of the mid values come out very well) , then it would stand to reason that using 0.75Z and 0.75Y or using 1.5Z and 1.5Y likely would have led to the similar success, and similar results.
Moreover, it is quite reasonable to assume that since light is relative, a painting produced in the 1.5 context, when lit with 0.75Y, should match the still life lit at 0.75Z.
At some lower levels of dimness, the eye is not so good at determining value differences, likewise, overbearing brightness leading one to squint, is also not conducive to painting. A novice will have a harder time with this than an experienced painter with a highly trained eye.
Now Keep an Open mind...
Idea: Capture more subtlety of range in the subject by painting with higher dynamic range (HDR).
In one variation, one merely uses the brightest Z and Y lights (effectively a higher dynamic range) which are not counter productive to painting, this should enable viewing and discerning more subtle variations which results in slightly more realistic results even when viewed under normal light. Beginners using color checking, would more easily see variations which otherwise might look "all the same".
In a second variation, the shadowbox and studio lights are varied, proportionally in the same amount, to keep the level of various parts being painted closer to the "sweet spot" for seeing and painting. In this example, one could use 2.0Z and 2.0Y for the darkest parts and the mid-values, and 0.5Z and 0.5Y for the lightest parts of the work... or whatever other combination works best.
PS: The same principle should be applicable to painting from a photo, but with limits as photo blacks are not true black, whereas shadowbox black is limited only by how well you can control lighting (using for example... a black paint in and around the studio and shadow box).