I love zorin OS, but I love KDE plasma too. So, I'd like to create a zorin-kde build.
I have some questions:
Have a nice Day.
Gday @SignorCastello , Try searching the forum as there are several topic's.
Try this to start with.
Look here for system requirements,
Best advice is " Try " core , then " Try " Lite,
prior to a full install, Note that thing's may run a little slower via usb drive , but runs quiet adequate for testing & get the feel of the OS.
Thanks @Ocka for interesting about the topic, thanks for the guide! Now I know the answer to the 4° question. But for the others?
Also try in the Customizing section
@storm has been making theme's lately & would be a good one to talk to. There are several other's that have diff theme's/desktop enviroments, they maybe offline atm.
i think i covered all 4 question's, some answers are within the link's.
eg: do i install first & thing's to do.... there is alot to learn & master what needs to be done
Dear Ocka,
for example you don't talk about this.
Yes, I know Storm. He makes a lot of good themes (the red ones are pure magic, and I wonder if they work for KDE too... @Storm)
I haven't any luck getting my themes to work with KDE 
They always turns out blank and noone can tell me why KDE is behaving like this...
They work in GNome, mate, cinnamon, deepin (qt), xfce etc.
yes in this link
you will see specs needed for Core & Lite
first try in the first link
Then try searching for more similar topic's in customizing etc. 
Ok, but I'm asking (e.g. @Aravisian, do you know this?) if it changes something between the two editions, when using the same D.E.
It would have been useful to have full details of your "low end spec" machine to give a sufficient answer. As an example my good lady's machine, a rig I put together in 2006, is maxed out at 2 Gb RAM with a single core AMD Athlon64 processor and EVGA silent cooled AGP 8x 256 Mb nVidia card so can only run xfce version of MX-Linux and not the KDE version.
samsung sf-310
it has a nvidia card but it's unsupported, so integrated graphics, 4g ram, dual core intel i5 3rd gen I think.
I'm sure I can run kde, rn I'm on manjaro kde, but I cannot use anything but zorin. Should I download the core or the lite? then I'll install kde and use only that.
The only difference you would see would be the amount of space taken up on the drive.
Since you are planning to install a D.E., it is that D.E. that would determine the performance of the machine.
Core is a bit larger than Lite; so you may opt for Zorin OS Lite just to have a smaller base footprint.
Yes, this is how I would do it if it was me. It would be safer and simpler than modifying the .iso prior to installing Zorin OS.
I cannot think of anything particular that stands out as a warning. Installing Plasma D.E. is pretty straightforward.
Plasma runs more lightly than Gnome. This is likely most optimized in the latest Plasma version.
I run plasma on Zorin, now for about a year and a half. It uses less ram than gnome (for me anyway). You may want to disable some of the effects/behaviors if it's too slow on your system.
I did the sudo apt install kde-full. This also gives you the qt apps for terminal, text editor and other such gnome counterparts. If you don't want these (i only use some of them myself), you could use the sudo apt install kde-plasma-desktop which should give you the DE and required dependencies, without the QT apps.
Either way, you can use the gnome and gnome-based applications while in plasma. This also opens other software up to you without having to worry about installing the QT libraries.
Remember and take note of the command you use to install. If you later choose to remove it, you can use the remove version of the install command.
I'll install the kde-full package. Then, could I remove gnome/xfce?
You can remove xfce without breaking anything, you CANNOT remove gnome. This would remove the gtk libraries and a lot of system applications dependencies.
This is dependent on whether you had core or lite to begin with!
If you had lite, it isn't recommended to remove xfce, if core, don't remove gnome.
I'll proceed in this way:
That's a solid plan. While it may annoy and take space to leave gnome, since there aren't QT variants of the Zorin software and modifications/ configurations, they need to stay, so gnome does as well.
I hope you enjoy your journey. Let us know how it works for you, and of course, any issues.
We're talking about Zorin os, of course I will!