Huawei MATE 9 Use Manual page 196

Enabling shortcuts for accessibility features
Use the power button to quickly enable accessibility features.
1
Open Settings.
2
Touch Advanced settings > Accessibility and select Accessibility shortcut.
3
Switch on Accessibility shortcut. You can enable accessibility features in two ways:
a
Hold down the power button until you hear a confirmation tone or your phone vibrates.
l
b
Touch and hold the screen with two fingers until you hear a confirmation tone.
System Features and Settings
190