On the assignment of axial and equatorial to substiuents of polyhexacyclics
The structure you have drawn where X = Y = Z = H is known as adamantane, C10H16. It has 3 degrees of unsaturation but visually appears to have 4 rings. Once 3 rings have been defined (rings A, B and C), then all C-C bonds have been accounted for. Put another way, you only need to erase three C-C bonds and add hydrogen to obtain a saturated, acyclic hydrocarbon, C10H22.
In structure 1 ring A is highlighted in red with X and Y equatorial to ring A. In structure 2 substituents X and Z are both axial to ring B. Structure 3 has the configuration of the Z substituent changed to equatorial relative to ring B. Ring C bears the same relationship to ring A as ring B does to ring A. Therefore in structure 4, substituent Y is axial to ring C. Now locate ring "D" and define equatorial/axial relationships of the Z substituent to ring "D" in structures 1 - 4.