YZ and Z1 are the same color. They used the Z1 code on Super Duty trucks. The F-150's and cars used the YZ code. Believe me, I know the color all too well.
Next time give R-M or Glasurit a shot. Both BASF products, and Glasurit is considered the premier paint. Many of the top car builders (Foose, Trepanier, etc.) use Glasurit exclusively.