Here are some tips to help
Can't hear others?
Check your speakers/headset
Is your volume turned up enough?
If your speakers are external, are they plugged in securely and switched on?
Is the correct speaker or headset selected? Check your settings.
Are you hearing an echo? If using external speakers position them further away from your computer ad reduce the volume. A headset or headphones might get ride of the echo.
Others can't hear you?
Check your microphone, is it plugged in securely and switched on?
Is your microphone muted? Check your device's audio setting.
Is Zoom using the correct microphone?
Is correct microphone selected? Check correct audio input selected in settings.
Is other software using the microphone? Quit other applications, a computer reboot maybe required.
Check your web camera.
If using an external camera, is it plugged in securely and switched on?
Is correct camera selected? Check correct camera selected in settings.
Is other software using the camera? Quit any other applications, a computer reboot may also be required.
Poor image or sound quality?
Check your internet connection.
Are others on the network using lots of bandwitdh, ie other video calls in progress?
Is your modem/router working properly?
Move closer to the access point, ideally you have a line of sight and are close.
If you would like to test your internet connection and setup using Zoom click here.