Unfortunately, it is not possible to texture the mesh in real-time with how the spatial mapping is made within the ZED SDK. For the moment, the texturing is only made at the end of the mapping, therefore it's not possible to get it during the mapping.
However, instead of generating a textured mesh, you can use the fused point cloud, which displays textured points in real-time.
You can find all the information regarding spatial analysis and mesh texturing here: https://www.stereolabs.com/docs/tutorials/spatial-mapping/