Two great choices.
Here is a look at their specifications, side-by-side.
They are an even match as far as video capability.
I see no difference in image quality.
The one thing that jumps out at you from the specifications is that the Casio Z750 has manual controls:
These are very important if you want to take photos in difficult to photograph situations.
Since you have your choices down to two, I would head for the nearest camera merchant and get my hands on both. This will usually make up your mind for you. The look and feel of a camera in your hands will probably cause your to pick one over the other.
One good thing about these two cameras, you can't make a mistake; no matter which you choose.
After spending hours researching, I think I have narrowed down my dissision to the Casio EX-Z750 and the Nikon Coolpix 7900. I just wanted to get feed back on both. I am looking for a good camera with image quality and video capabilities, though not going to video the world. Any feed back or opinions, and suggestions are appreciated.