Brightness

I have installed zorin os 16 pro, but brightness key not working, and there is no option on panel as well as setting for increase the brightness ,

Dell Laptop, core i3, Inspiron 15 3000,

If you search the forum, box at the top right of the page, you will find [HOW TO] Enable Screen Brightness Function Key Combinations (Zorin 15.3).

While this was for zorin 15.3, it may still assist you.

What model computer are you running? What year was it manufactured? If you use your zorin download link it can provide you with 16.2 which includes newer kernel and firmware, possibly resolving this. Did you check the sha256 checksum against the sum listed on the official site?

You can get the checksum for the iso by loading into Linux, opening terminal and typing sha256sum <directory-where-iso-is>/zorin-core-pro-16.2-64bit.iso

You could also see if installing this gnome extension helps:

https://extensions.gnome.org/extension/231/brightness-control/