I would like to modify the CTI Flex theme but would prefer to keep my changes as maintainable as possible. CTI Flex is already a Zen (7-x.3-x) sub-theme.
I have used the Zen starterkit in the past to create a Zen sub-theme, but never a sub-theme of another sub-theme.
How do I create a sub-theme of using another Zen sub-theme as a start point?