I am having zero luck searching for work or information regarding a version 6 responsive zen sub theme. Rather than recreate the wheel I thought I would inquire here for any leads. This is also my first time posting to stack so apologies in advance if this question is better asked elsewhere.
I am also wondering if the v6 Zen base kit isn't a good candidate for responsive design due to the already heavy use of stylesheets.
Zen base theme has been (mostly?) made responsive.
To build a responsive sub-theme with Zen, you'll need Zen Grids
Edit: Just noticed you were asking about D6, so YMMV. If you're building a responsive site it's likely a much better idea to just BTB and upgrade to D7.