When using the word 'zone' if you are referring to one of the places inside the FluidGrid you set up, and, now you want it centered in that part (e.g. "zone"), then add the standard wiki syntax for centering anything, double colons on each end of the Plugin Carousel, for example:
::this text is centered::
which would look like this:
I'm guessing you know this syntax, but maybe haven't tried it in this configuration.
I have not tried this with Carousel as I don't use it anymore, but there is a good possibility it will work.