Hi, I'm new to the forum. Would it be a good idea to install zorin os core on an old core 2 duo machine with an SSD and 4 gigs of ram? Or should I go xfce with Lite? I really like GNOME. But I'm willing to go xfce if GNOME would lead to lagginess or freezes or what have you.
My dad will be using it for casual web browsing and photo viewing and stuff. And I don't know the exact model of the CPU but it's probably a 64 bit version.
Four gigs of Ram - is a bit of a pinch. I think you may see some slowness but for casual browsing, photo viewing or editing, watching a video or two... Core should be able to do fine.
I believe XFCE (lite) may be a little lighter on the CPU and other resources.
What you might do is try both in one go, if you don't mind configuring your Zorin OS install a bit. You can install Core and test it out. Then open a terminal and install the XFCE4 desktop:
sudo apt install xfce4
This will likely lead to you installing and setting up LightDM instead of GDM3 - Say yes at the prompts - when complete, log out and log in - click the DESKTOP chooser icon on the upper Right side of the toolbar (The icon itself will be the leftmost icon in that area) and choose XFCE desktop.
Then test that.
This option will allow you to explore how both D.E.'s function within just One Install. If you prefer one D.E. over the other, you can just stay logged into that one. Or, remove XFCE4 if it doesn't make the cut.
Oh right, thank you so much. I had completely forgotten multiple DE's could be installed. Thanks for detailing out the procedure. I'm kinda tight on internet data, so this would help me out tremendously.
Okay, now a noob question, cause I've never done this before. When I install xfce and run it, will I get xfce apps like thunar, or do the gnome apps work with the xfce de?
Installing XFCE4 will also install Thunar and XFCE desktop apps.
You might want to install additional xfce apps that round out the desktop with
sudo apt install xfce4-goodies
And if you want the Zorin OS menu
sudo apt install xfce4-zorinmenulite-plugin
Alright, thanks a lot dude. 
I can't disagree with that. I have an old Core2Duo which had 2.5G RAM and ran 15.3 Core well for those moderate tasks, no serious gaming, CAD or modelling etc. I have now upgaded it to 4GB RAM but see little difference. You should be fine with Lite or Core. You can see which DE you prefer.