In DFP you still create the unique Ad units based on size. Because we have the SZ in the name, we can use the same PL number. See below
The only difference:
a. You add both ad sizes to the line
b. You upload a creative passback in each of the sizes
c. Be sure you select "As Manay as Possible" creative
You do the same with the ADX Line.
- Target the multiple ads sizes
- Create multiple ADX creatives
Ad Unit Mapping to Placements
For mapping to the placements in DFP, be sure to select all the ad units and add.