No, I'm not really seeing what you're referring to.
The slope of the hood is similar -- but that is expected since pedestrian safety concerns and fuel economy (aerodynamics) are pretty much dictating that all cars converge on the same "ideal" shape, at the front. The rear lines are completely different.
The Mercedes headlights are completely different. Mazda and Infiniti both use a more slender design, but that's simply a trend. The actual execution of the design is completely different between the brands.
The interior is effectively completely different. You must extremely limit your scope to find similarities. For example, the steering wheels have similar -- but not identical -- spokes. However, the steering wheel centers are quite different between Mazda and Infiniti/Mercedes. The HVAC controls have buttons flanked by two dials -- but that design is in so many cars that it could hardly be an identifying feature. Even so, the Mazda execution is definitely "unique" from the Infiniti/Mercedes part, which was obviously shared. Dash design, instrument cluster, air vents, radio, infotainment screen -- all completely unique on the Mazda.
I see where Infiniti is using Mercedes parts... I don't see where Mazda would be.
2018 Infiniti QX30 Premium AWD - Majestic White
2019 Volvo XC60 T6 AWD Inscription - Onyx Black Metallic
2018 Honda Gold Wing Tour - Pearl White