Firmware Asus Zenfone 3s Max ZC521TL

OS: Android 7 (Nougat); ZenUI 3

CPU: Octa-core (4x1.5 GHz Cortex-A53 & 4x1.0 GHz Cortex-A53)

Display: 5.2" inc

Camera: 13 MP, Single

Before flashing, you need
Create a full backup of the firmware.
The battery must be 100% charged.

1. Flashing your phone using CWM Recovery
2. Flashing the phone using TWRP Recovery
3. Flashing the phone using Fastboot

1. Phone flashing using CWM Recovery
The rich functionality of CWM Recovery www.clockworkmod.com allows you to perform many manipulations with the device, including rolling the firmware. By default, stock Recovery is installed in the devices, which means that first you need to install the ClockWorkMod Recovery utility itself.
The general firmware process described below is for ZIP files. Instructions: - Download the required firmware and place it on the phone's memory card.
- After that, turn off your smartphone.
- Press a certain combination of buttons on the phone, the combination may vary depending on the manufacturer of the phone. If you do not know the required combination, try pressing the following keys.
- Press the buttons: Power + Volume up (or Volume Down) (+Home) simultaneously for 10 seconds.
- As a result, the phone will boot into Recovery mode.
- Use the volume buttons to navigate the menu, and use the Power button to select.
- Use the volume buttons to select 'Wipe data / factory reset'.
- From the Recovery mode menu, select 'Yes - delete all user data'.
- Highlight the 'Wipe cashe partition' and press the Power button.
- From the menu select 'Yes - Wipe cache' .
- From the Recovery mode menu select 'advanced' .
- From the menu select 'Wipe Dalvik Cache'.
- Highlight 'Yes - Wipe Dalvik Cache' and press the Power button.
Go back, press 'Go Back'.
- From the menu select 'mounts and storage' .
- Use the volume buttons to select 'format / system' .
- Highlight 'Yes - Format' and press the Power button.
Go back, press 'Go Back'.
- Select 'install zip from sdcard' from the menu.
- Choose 'choose zip from sdcard' .
- Highlight 'Yes - Install your firmware name' and press the Power button.
- Now from the Recovery mode menu select 'Reboot system now' .

2. Flashing the phone using TWRP Recovery
For those who prefer working with the utility in the form of TWRP Recovery, the following instructions for the step-by-step installation of the update in the form of a ZIP archive are offered:
- Upload the file with the firmware image to the phone's memory card.
- Go to TWRP recovery. This is done by analogy with CWM.
- Perform a factory reset. When finished cleaning the phone, return to the original menu by pressing the 'Back' key.
- In the main menu, select 'Install' and find the previously downloaded firmware image. Click on it by dragging the slider to the side.
- The process of flashing the phone will take 2-3 minutes.
- Upon completion, the utility will automatically display a message about successful flashing. Click on the 'Reboot System' item, and reboot the device.

3. Flashing the phone using Fastboot
A universal tool for flashing Android smartphones using a PC is the Fastboot utility. It is part of the SDK Platform Tools, which means it is suitable for a large number of devices.
Before starting the firmware, you need to get access to the system kernel. Very often, many manufacturers block this system parameter, not wanting users to change the system files of their firmware images with their own hands. To do this, you need to unblock Bootloader. To do this, you need to study the detailed instructions for configuring and managing the command line. Before starting the firmware using a computer, do not forget to enable USB debugging of the device in the engineering settings of the device.
- Copy the .zip archive with the image, and place it in the folder with 'ADB'
- Put your smartphone in fastboot mode and write the prompt in the command line: fastbooflash zip filename.zip, where filename.zip is the name of your firmware.
- After the end of the installation, reboot your phone.

Thomas Nilan
Smartphone Expert

Thomas Nilan is a mobile phone expert with in-depth knowledge of the Android and iOS operating systems, who understands the settings of various hidden features that allow you to expand the capabilities of your smartphone, as well as get information about what is going on inside the phone for future repairs. He is an authority in his field, which has allowed him to become a ghostwriter for several technology publications, and he enjoys writing small mobile applications for testing smartphones.