(I just HAD to add my two cents' worth here -- we used to hike to Lingenfeld... so this brings back memories.)

I'd go with your idea "rezoning" rather than planning since the re in rezoning indicates that a change in zoning status might have been contemplated, and that's the sense I get from the prefix über in Überplanung. Knowing Lingenfeld and its environs, I wouldn't use the phrase "urban development", either - it is quite rural and would require a whole lot of development in order to become anything even close to urban... :-)

HTH!