Actually, if a plant is recommended for zone 6 minimum temp and zone 11 maximum recommended, then yes, you do[ have it right; that plant ought to thrive in all the zones in between.
SedonaDebbie, for many spring bulbs, summer dry is as important as winter cold. Many plants (not just some bulbs) respond to dual or multiple triggers for seasonal changes. Often, these triggers will work in tandem, so that together, neither needs to be as extreme as either working alone.
You apparently still have a seasonal temperature change that is enough because you have low humidity and summer dry to work in tandem with the seasonal temperature change. The same zone in Florida does not. Similarly, growers in cold zones have enough cold to do the job by itself, even though their summers are not hot and dry.
