Bronco often just inserts a safety as the buck ILB. That is the only adjustment to the zones of the 3-4. Having a safety at buck simply gives the defense someone who is a little quicker to cover the routes that slot receivers usually run.

Bronco's dime is often to put another safety or big corner at the field-side OLB. That provides more speed to cover both RBs in the flats as well as WRs. The zones don't change with this alteration.