There's a difference between a shepherd and a preacher, and shepherds are not called to preach but to shepherd Greek word "poimen - to protect" and preachers are called to preach and not shepherd. In Ephesians 4:11 there's no mention of preaching or preachers and that's because Saints don't need preaching but equipping. And according to the Greek and many Greek scholars shepherds and teachers are one of the same which should have been translated "teaching shepherds".