Yield , Multi-year averaged vegetation, slope/topography -  looks like good datasets to start. 

You can aggregate them and set weights for each data layer in our software. Blog - Multi-layer analytics in precision agriculture.

After zones are created, the rates could be set. I'm not sure about VR tillage values, probably it should be 0 and 1.

You can drop me an email - we'll assist you with it for free.