Hi Daniel,
Your understanding is correct. In your case ZMATERIAL will behave exactly as 0MATERIAL. You do not have to load any master data since ZMATERIAL references 0MATERIAL.
The only exception is using navigational attributes. All attributes of the referenced 0MATERIAL are automatically available as display attributes in ZMATERIAL. You can switch on navigational attributes in ZMATERIAL with the prerequisite that the attribute is a navigational attribute in 0MATERIAL.
E.g. 0PROFIT_CTR is a navigational attribute of 0MATERIAL. It can be switched on as navigational attribute in ZMATERIAL. However, 0COMP_CODE is only a display attribute in 0MATERIAL. You can only switch it on as navigational attribute if it is done also in 0MATERIAL.
Best regards,
Sander