Zorin is running very slow

[zabadabadoo]

I am not sure kernel version would affect performance unless it was a bad update for your particular machine. Also remember latest and greatest kernel is not always the Best kernel, so don't go chasing that tiger as it may bite.

I assume you have Z16 Core. Which kernel version are you running?
Did slow performance start after a kernel update?

Some things to check and tell us about:
Disks: How much free space do you have in root?
How much RAM do you have?

EDIT
You may also want to see if your log files are getting big and prune them. See this:

Using the Terminal Emulator in Linux Distros

I find it useful to write down commands or series of commands in a simple notebook to refer to when needed for specific tasks. That is especially helpful for occasional housekeeping tasks and running CLI utilities e.g. Rkhunter etc. Maybe this thread can also become a "notebook" of useful commands. The CLI is powerful, but should not be frightning to the user. I would reitterate what others have mentioned on the forum elsewhere. Read the screen output carefully before clicking "Y". It is like …