To enter the Recovery Menu on Zorin OS if using Legacy (MBR) boot, you can hold or tap the Left Shift key at boot to be offered the Advanced Options for Zorin Grub menu.
If using EFI Boot, then tap the esc key vigorously. Some users report that the tab key worked, instead.
You might think that this is pretty straight-forward. However...
- Some BIOS are programmed to ignore a key being held down, as it is assumed to be pressed by accident or a stuck key. Cat on keyboard, coffee... The BIOS programmers felt that it is preferable to have a smooth boot experience.
- If your grub file is set to GRUB_TIMEOUT=0, then it is a fair chance you will have great difficulty in hitting that millisecond that the option is there for the recovery menu keypress to be registered.
- Sometimes, it is all about timing.
For future reference: While you may feel like you can decrease your boot time by setting grub timeout to zero - it is best not to as if you need the recovery menu - you will have painted yourself into a corner.
But in the end - Patience is the key. It may take repeated attempts and tapping the key til your face is red and your wrists are on the Carpal Tunnel Endangered List... But if getting to the Recovery Menu does not work the first time; Don't Give Up.
Crack your knuckles... take a deep breath... And Show that Left Shift Key or escape who Commands It.