I like the design and use of color in #5. I also like the simplicity and the prominence of Zanthia - I could use this for a lot of other sub-businesses under the Zanthia name.
One thing I would like to see with this logo is a single color for the word Zanthia to see how it compares vs. the current colors (e.g., a solid dark or electric blue vs. the current faded coloring).
I do not like the slash through the z in #6. I prefer the colors in #5.