Problem with displaying colored map

[BenjaminSmith2]

So I'm working on displaying zip code maps of Los Angeles, CA and am running into a problem. I want to use the internal symbology to show attributes of each zip code color-coded into quintiles, but want to make three maps: one with the four counties, then a zoomed-in version for just LA and Orange Counties. However, I want the color coding to be the exact same on the overall map and the zoomed-in map. So: how can I display only zip codes in LA and Orange Counties but have the internal symbology mechanism calculate quintiles and their cutoff values using zip codes in San Bernardino and Riverside counties? 

[SteveCole]

Make a second copy of the zip code layer in your map but apply a definition query to it to only show the zip codes in San Bernardino and Riverside counties. Apply some sort of "plain" symbology for the features in that layer. Now adjust the layer order such that the  SB/Riverside zip code layer is directly above the LA/OC zip code layers in the Table of Contents.

The SB/Riverside zip code features will now "mask" out the quintile values without you having to eliminate them from the map.

Steve