First of the lens is the optics. Sensor is the silicon under it, what film was in the old analog days. Both have effect on the outcome.
I have no plans to open the phone but IMX258 looks like to fit within the specifications well. Sony dominates the sensor market so it's very unlikely to find anything else there.
Regarding the optics, as there is are not a typically blue "ZEISS" logo, but yet it's printed so they are somehow involved. I don't believe in manufacturing in Germany as they barely do their own top of the line lenses there anymore. Maybe Zeiss machinery and tools might have been used for creating these lenses, or maybe licensed design etc. Probably no classic radiocative micro-contrast woodoo, but it doesn't matter, (yet it would be fun to hear a story what they actually provide). Whenever Zeiss optics are involved they tend to help providing pleasant image rendering to the human eye, not necessarily a benchmark winner in synthetic sharpness tests.
Todays smartphone/small image sensors are way ahead their larger brothers, I would not bet on an magical jumps in technolog, rest is physics. A physically bigger sensor will help collecting more light, and there for increase low light performance, and possibly also some dynamic range.
These dual sensors RGB+monochrome is of course just some software magic algorithms pushing more contrast into the images. Maybe we see layered sensors soon, like Foveon or even a triple sensors that Red, Blue and Green each get their own. But again, it's up to Sony to cook the sensor magic.
