So, please be patient with me, I'm very new at this. Tried to follow the previous answers to this question and none have worked, most answers are outdated acktually. Just now that it has something to do with "installing the required dependencies from https://mint.pkgs.org/21.3/mint-backport-amd64 and the nemo extensions from here Releases · linuxmint/nemo-extensions · GitHub" but have no idea how. Also the first link in the aswer is broken.
(EDIT #1: Zorin OS 18 running nemo 6.0.2)
The version matters; Are you on Zorin OS 17 or Zorin OS 18?
Also
nemo --version
You could try to download it from here:
Choose the last entry on the page for xia:
nemo-preview_6.4.0+xia_amd64.deb
Edit: Don't use this package. It doesn't fit to your nemo version.
Need to match to the version of Nemo the user has.
In Noble, it provides 6.0.2
This is also trickier because a variety of Mint Only Dependencies (xreader, xdocument) need to obtained and installed, too.
Is this one better for Zorin 18?
nemo-preview_6.0.1+virginia_amd64.deb
It is really complicated to install the nemo preview extension.
Maybe you could try to install gnome-sushi for the default filemanager nautilus? It is contained in ubuntu 24.04 repo. I haven't tried yet.
Nautilus really didn't match my necessities in file management thus the jump to Nemo...
"Unable to install nemo-preview" with nemo-preview_6.0.1+virginia_amd64.deb package.
Details: "The following packages have unmet dependencies:
nemo-preview: Depends: gir1.2-xreader but it is not installable"
Yes, you also need dependencies, the downloaded file is only one part of the installation.
Thunar and nemo offer more possibilities by default, that's true. For nautilus you can e.g. install nautilus-actions and nautilus-admin to adapt it and to be more flexible. But it is more difficult than with nemo.
Yeah... just took a look at apparently nautilus-actions was abandoned. Man, this stuff is really complicated. 
Maybe I can go this way. Do you have some tip on how to do it?
gir1.2-xreader
libxreaderdocument3
libxreaderview3
These dependencies and possibly others are needed.
The easiest way is to temporarily add the Mint repo:
sudo gpg --keyserver keyserver.ubuntu.com --recv-keys A6616109451BBBF2
sudo gpg --export A6616109451BBBF2 | sudo tee /etc/apt/trusted.gpg.d/linux-mint.gpg > /dev/null
echo "deb http://packages.linuxmint.com zara main upstream import backport" | sudo tee /etc/apt/sources.list.d/mint-zara.list
sudo apt update && sudo apt install nemo-preview
Once installed, remove the Mint Repo to prevent conflicts with Zorin OS packaging:
sudo rm /etc/apt/sources.list.d/mint-zara.list
sudo rm /etc/apt/trusted.gpg.d/linux-mint.gpg
EDIT: I just tested this and it does work:
The following additional packages will be installed:
gir1.2-xreader libxreaderdocument3 libxreaderview3
The following NEW packages will be installed:
gir1.2-xreader libxreaderdocument3 libxreaderview3
The following packages will be upgraded:
nemo-preview
1 upgraded, 3 newly installed, 0 to remove and 44 not upgraded.
Need to get 424 kB of archives.
After this operation, 1,625 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://packages.linuxmint.com zara/backport amd64 libxreaderdocument3 amd64 4.4.0+zara [205 kB]
Get:2 http://packages.linuxmint.com zara/backport amd64 libxreaderview3 amd64 4.4.0+zara [109 kB]
Get:3 http://packages.linuxmint.com zara/backport amd64 gir1.2-xreader amd64 4.4.0+zara [63.0 kB]
Get:4 http://packages.linuxmint.com zara/backport amd64 nemo-preview amd64 6.4.0+xia [47.5 kB]
Fetched 424 kB in 1s (708 kB/s)
Selecting previously unselected package libxreaderdocument3.
(Reading database ... 448434 files and directories currently installed.)
Preparing to unpack .../libxreaderdocument3_4.4.0+zara_amd64.deb ...
Unpacking libxreaderdocument3 (4.4.0+zara) ...
Selecting previously unselected package libxreaderview3.
Preparing to unpack .../libxreaderview3_4.4.0+zara_amd64.deb ...
Unpacking libxreaderview3 (4.4.0+zara) ...
Selecting previously unselected package gir1.2-xreader.
Preparing to unpack .../gir1.2-xreader_4.4.0+zara_amd64.deb ...
Unpacking gir1.2-xreader (4.4.0+zara) ...
Preparing to unpack .../nemo-preview_6.4.0+xia_amd64.deb ...
Unpacking nemo-preview (6.4.0+xia) over (5.6.0-2) ...
Setting up libxreaderdocument3 (4.4.0+zara) ...
Setting up libxreaderview3 (4.4.0+zara) ...
Setting up gir1.2-xreader (4.4.0+zara) ...
Setting up nemo-preview (6.4.0+xia) ...
Processing triggers for libc-bin (2.39-0ubuntu8.6) ...
Thank you very much. Will try that and post any updates here. Thanks wonderful Zorin people.
That is an extension you can use to get nautilus-actions. To install it on Zorin 17.3 I downloaded the .deb file
It is much easier in nemo and thunar. There you don't need extensions for modules/custom-actions.