All-screen phones look cool, but they challenge the manufacturer to find a place to put front cameras, sensors and other hardware. That's why we see bezels on some phones and notches on others. It's not clear what Lenovo plans to do with the front camera on the Lenovo Z5. Cheng's post claims that "four technological breakthroughs" and "18 patented technologies" were made for the phone, but doesn't go into details. One of the first smartphones to launch with an edge-to-edge display was the Xiaomi Mi Mix. It launched with next to no bezel or notch, leaving many to wonder where the earpiece would be. What Xiaomi managed to do was use what it calls "cantilever piezoelectric ceramic acoustic technology." Basically, it's a component that converts electrical energy into mechanical energy to transfer to the phone's internal metal frame, which then vibrates to create sound. It's possible the Z5 relies on a similar technology, or bone conduction technology found in many headphones and some smartphones.
Aside from the front-facing camera and ambient light sensors, the other components that are typically found on the front of smartphones are relatively easy to drag-and-drop to different locations. For example, the speakers in the Z5 are likely bottom facing and the navigation controls are almost certainly software based. The question is whether or not it's worth having a true all-screen smartphone if it means there's no front-facing camera, ambient light sensors, or stereo speakers.