ZTK suffers from two main issues:
1) They can't decide which market they want to appeal to - as a result, they get a couple of points in Greensboro and a couple in Raleigh. Enough cume to make some money if they can convince the buyers (agencies) to combine the ratings.
2) The key demo for WSJS is very slow to change - or even notice there is a reason to change. If you look at sharing, you find WSJS shares way more with WFDD, WMQX, and WTQR than with ZTK. The secret for ZTK would be to develop a direct mail campaign at WSJS's hot zips.
SJS may be listing, but the audience is not switching to ZTK in large numbers.