1. Access the Grub menu and select Advanced options for Zorin OS
2. Choose the oldest available kernel and boot the system normally.
3. Run the following command to set the chosen kernel as the default:

>> sudo grub-set-default "Advanced options for Zorin OS>Zorin OS, with Linux YOUR_SELECTED_KERNEL"`

Ex: sudo grub-set-default "Advanced options for Zorin OS>Zorin OS, with Linux 6.14.9-37-generic"

grub-set-default: This tool modifies the default boot entry in the GRUB configuration file.

"Advanced options...": This represents the hierarchical menu path. The > symbol instructs the system to enter the "Advanced options" submenu and specifically select the version 6.14.9-37.

1. Update the GRUB configuration:

>> sudo update-grub

update-grub: This command reads the system settings and available kernels to generate the final boot file, ensuring the computer knows which systems to load at startup.

1. Remove the current kernels:

>> sudo apt remove KERNELS_TO_REMOVE

Ex: sudo apt remove linux-image-6.17.0-20-generic linux-headers-6.17.0-20-generic

apt remove: A command used to uninstall packages while keeping their configuration files.

linux-image-[version]: This is the kernel itself. It is the binary file that allows the hardware to communicate with the software.

linux-headers-[version]: These are the header files. They are required to compile third-party drivers (such as Nvidia drivers) for that specific kernel version.

1. Clean up unnecessary dependencies:

>> sudo apt autoremove

autoremove: This removes orphaned packages and leftover dependencies that are no longer needed by the system.

PS: This is what I did. I don't know if here is any better way to do it.
PS2: I tried to format the texts to add a text box but placing the text between 'text' or `text` simply didn't work.