Well, I already know the history behind their issues but here's mine.
I have around 30-40 Dell D630's that I put Zorin OS 9 on (Ubuntu based). They run great, quick and snappy compared to windows, however there are two different kinds. One is running Intel Crystaline graphics the other is a Gallium 0.4 NV86 chip. The intel's run just fine, however the majority are running the Nvidia chip, so the main issue is that when ever the computer is put to sleep the screen's backlight never resumes. Been having a headache trying to find a solution but to no avail.
I'm sure someone more linux savy than myself could figure this one out.
You're using the open source driver. You'll probably be better off with the NVIDIA drivers.
Ubuntu has a nice application called Jockey to help install the NVIDIA drivers (recently moved to System Settings -> Software & Updates -> Additional Drivers). I'm not sure if it exists in Zorin OS as well. The application handily uninstalled and blacklisted the open source driver before installing the NVIDIA one.
Otherwise, you can try installing the drivers by downloading them from the NVIDIA site directly and going through the installation process. Make sure you get the right driver versions for your GPU. Some GPUs have been moved to legacy drivers recently.
Check this to see if you need the legacy drivers or not http://www.nvidia.com/object/IO_32667.html
I think on ubuntu based distros legacy drivers are listed as nvidia-<number> you can steach for them and install the correct on.
(what an odd choice of distro..? I couldn't find any documentation, or the location of there software repo)
edit: you might need to remove the free software drivers if they conflict, which they might. alternatively add modprobe.blacklist=nouveau to the linux line in grub. You will also need to configure X to use the nvidia driver if you dont know that already.. ?