1. This is a 3+2 cable. Three cores are the power conductors, also known as the main conductors. The other two cores are the ground and neutral conductors, primarily used for grounding and three-phase unbalanced current. Their cross-section doesn't need to be the same size as the main conductors, primarily to save material.
2. ZR-YJV is not a fire-resistant cable; it's a general flame-retardant cable. It automatically extinguishes when separated from the ignition source, effectively preventing combustion. NH, on the other hand, is a fire-resistant cable that can maintain power at temperatures exceeding 700°C, but it's not necessarily flame-retardant.
