The ZenFone 5z has a 6.2-inch, 2246x1080 IPS LCD. The display has an aspect ratio of 18.7:9, which is a bit shorter than the display on the OnePlus 6 and the Huawei Nova 3 and same as the display on the Poco F1.
Numbers aside, the display on the ZenFone 5z is top notch (no pun intended). Out of the box, the display is calibrated for the DCI-P3 color space, which isn't ideal. However, with the flick of a switch from the display settings, it can be changed to sRGB. With a few other adjustments (disabling screen color optimization mode and increasing the color temperature), you can get near perfect color calibration.
The display does not have the perfect black levels of the AMOLED display on the OnePlus 6. It also doesn't get particularly bright and might be a bit hard to see on a bright day. But aside from that, this is an excellent display, and it's good to see Asus provide not just good color values out of the box but also plenty of options for further manual adjustments.
The ZenFone 5z has a 3300mAh battery. The battery life can best be described as acceptable. The ZenFone 5z should get you through most days, but if you're a heavy user, you should consider something with a larger battery, such as the Poco F1.
The ZenFone 5z does support Quick Charge 3.0 and comes with a compatible 18W charger in the box. QC isn't really the fastest fast charging standard around, and the phone takes about two hours to charge completely.
The ZenFone 5z has a stereo speaker system, which uses the bottom firing speaker and the earpiece as is common these days.
Unfortunately, while the audio quality isn't bad by any means, the speakers tend to sound extremely imbalanced at times. There is a vast difference in the frequency responses of the two speakers, with the bottom firing speaker producing the bass and the mids and the earpiece speaker only being able to handle the higher frequencies.
The two speakers handle different parts of the audio spectrum, so the sound feels like its bouncing back and forth between them when someone is talking as different parts of their voice are picked up by a different speaker.
This is more noticeable when holding the phone close to your face at about a foot away. When holding the phone further away, the sound from the two speakers melds together, and it's harder to tell them apart but up close the sound is extremely imbalanced, and you can tell two very different speakers are working here.
One good thing that Asus has done is that the speakers tend to flip channels when you rotate the device so left channel audio always comes from the left side regardless of how you hold the phone, something not many Android OEMs bother implementing.