What's the difference between Ubuntu and Zorin?

Is Zorin just Ubuntu with a custom Gnome theme?

A quick Google search brought up this website, haven’t read a lot of it but may help.

Zorin tries to work a lot like Windows to ease the transition to Linux.

I just read through the whole review and there were no real differences mentioned. Unfortunately this is fairly typical of the other reviews of ubuntu vs. zorin I’ve found.