Some additional resources that may be useful for your project:
The DIY Zoning Project
Manual Zr - Residential Zoning
http://www.contractorresource.com/manual-zr-residential-zoning.html?gdftrk=gdfV27686_a_7c1308_a_7c3363_a_7cACCA_827&gclid=CMHv8aqc3bsCFclQOgodHX0AAg