Unable to install Zorin onto my Desktop PC

You already have two operating systems installed on one drive— That may be where we can find an issue.
You cannot have more than Four Primary Partitions on a drive- this is a Motherboard thing… It is not relevant to which Operating System.
If you have two already and Windows loves to use more than one partition all by itself, I would check how many Primary Partitions the drive has.

@Aravisian, Friend, Please go through my comments which was marked in bold.

I have Windows 10 on a 1TB HDD by Seagate. With all the partitions. Since,that is in UEFI mode, I can have more than 4 partitions. And in Windows I do have about 6 partitions,all of which are primary not logical or extended.
I have MX-Linux on a separate 500GB HDD by Seagate. Here I do have /, SWAP and /home as 3 separate partitions. This is also in UEFI mode.

I have a spare extra 500GB HDD by Seagate onto which I want to install Zorin Linux. That is completely BLANK and FREE.

Yes, i performed the operations on GRUB command line and Kernel line.
After booting(CTRL+X) , the SCREEN COMES BLANK. NOTHING IS SEEN.

I am sorry- but this is impossible.
I am not guessing, here... You simply CANNOT have more than Four Primary Paritions- At All.
However, you will see manufacturers use a hack to create "Sub-partitions" on machines that break one primary partition into several sub-partitions that on a partition manager look like Partitions. This is what you are seeing on your drive.
This limitation is set by the way MBR is and UEFI mode does not change that.

Since you have a separate HDD, this above should not be an issue for you, however. Is this HDD an External HDD? If so, you must be plugged into a verified 3.0 USB port. 2.0 will likely fail.

@Aravisian, Friend… You are taking about the MBR form of Partition table in a Disk,WHICH CAN HAVE ONLY 4 PARTITIONS NEVER MORE THAN THAT.

But,my Disk is under UEFI or rather GPT form of Partition table,where you could have ANY NUMBER of partitions ,THEORETICALLY.

Separate HDD is an internal drive NOT EXTERNAL.

Funny,thing is that I can install Zorin Linux with UGLY resolutions. 1024x768 only.
Whereas my monitor supports 1920x1080 FHD resolution.

Installation is done by choosing SAFE GRAPHICS mode. Even after upgrade and installing Radeon drivers,I cannot change resolution from 1024x768 to 1920x1080

No, EUFI does not allow more than Four Primary Partitions. You are looking at what I described above.

You can have up to 128 of these partitions. But only FOUR of them can be Bootable.

So,where does that conflict with installation of Zorin?

And what about the resolution change???

You are correct. I forgot for a moment that your HDD was Free and Clear. That is my fault.

How is that HDD connected?

Internally through sata Cable with one of the sata port of the motherboard

You clearly are not novice and know your stuff. The drive is connected through a proper cable.
Usually the errors you are seeing are Hardware related. Bad download, bad media, USB cable- things of that nature.
I am beginning to feel a bit stumped.

I’ve changed the USB drive.
Downloads were verified and found to be full okay.

Windows 10 and MX-Linux is running and performing as per standards. Fully okay. No issues.

Then what is the problem with ZORIN OS???

How much space did you free up for Zorin?

He has a SATA drive, 500 Gigs wiped and clear, he said.

@Aravisian, I have installed Zorin OS onto my PC(Partial Success).
That is because I need to Boot from Grub Menu of Zorin ,SUCCESSFULLY,only after I add ‘nomodeset’ at the end of Kernel line and subsequently pressing Ctrl+X.

The Desktop is UGLY with 1024x768 resolution, WHICH I CANNOT CHANGE.

How do I change it to 1920x1080 resolution??? THIS IS WHAT I NEED AS HELP!!!

natun-athiti, have you upgraded the drivers and kernel after install?

Yessss…

This is one of my snippet …

tabatiti@comparado:~$ su -
Password:
root@comparado:~# xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm
1024x768 76.00*
root@comparado:~#

I want to get rid of the 1024x768 resolution.
Please save me…

Ok, can you open a terminal and paste in:

xrandr --newmode "1920x1080" 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -HSync +Vsync

Then do

xrandr -q

Look for your graphics card name. It may be eDP or VGA-1 or HDMI-1 depending on what monitor you have and how it is connected.
Once you have the name, try to add the mode for 1920x1080 res
For Example on My Computer it would look like

xrandr --addmode HDMI-0 1920x1080

Replace the HDMI-0 with your monitor name

Just see this:–>
root@comparado:~# xrandr --newmode “1920x1080” 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -HSync +Vsync
xrandr: Failed to get size of gamma for output default
root@comparado:~# xrandr -q
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm
1024x768 76.00*
“1920x1080” (0x2e1) 172.800MHz -HSync +VSync
h: width 1920 start 2040 end 2248 total 2576 skew 0 clock 67.08KHz
v: height 1080 start 1081 end 1084 total 1118 clock 60.00Hz
root@comparado:~#
How do I proceed???

I see you are using su - above.

Do not use a root terminal to perform this operation.

After trying that, let's look to grub:

sudo nano /etc/default/grub

Can you paste the output of that here?

Again failing…
tabatiti@comparado:~$ xrandr --newmode “1920x1080” 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -HSync +Vsync
xrandr: Failed to get size of gamma for output default
X Error of failed request: BadName (named color or font does not exist)
Major opcode of failed request: 140 (RANDR)
Minor opcode of failed request: 16 (RRCreateMode)
Serial number of failed request: 19
Current serial number in output stream: 19
tabatiti@comparado:~$ xrandr -q
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm
1024x768 76.00*
“1920x1080” (0x2e1) 172.800MHz -HSync +VSync
h: width 1920 start 2040 end 2248 total 2576 skew 0 clock 67.08KHz
v: height 1080 start 1081 end 1084 total 1118 clock 60.00Hz
tabatiti@comparado:~$

Try restarting xserver

killall Xorg

Check to see if it is working.

Again, please paste output of sudo nano /etc/default/grub here

Which drivers are you using currently?