PTZ Controller v3 provides 4 ways to control PTZ camera Zoom.
4 ways to control Zoom:
- Click the button
or 
to pan left or pan right step by step. - Drag the circle bar
to adjust zoom continuously. - Use Keyboard Shortcuts,
for zoom in, 
for zoom out. - If joystick or gamepad is connected, you can also control zoom with joystick or gamepad.