revolve around vs zero in

revolve around

verb
  • To be connected with; to concern. 

zero in

verb
  • To concentrate or focus one's attention (on a task). 

  • To focus one's aim; to zoom in and center (on something). 

  • To converge (on). 

  • To successfully narrow down a search (for). 

How often have the words revolve around and zero in occurred in a corpus of books? (source: Google Ngram Viewer )