Another way is to save this as a python script and add it to your toolbox then put it in your model with the output of the select by location as a precondition
#### Created By: Frank
#### Created on: 03/22/2011
#### Description: Zooms to a selected elements in a layer of an MXd
## Set the necessary product code
import arcinfo # If you do not have an ArcInfo license change this
## Import arcpy module and environment module
import arcpy
import arcpy.mapping
## Sets the MXD file, if run out of ArcMap set the full path to the MXD file ex: "C:\Workspace\Parcel_Map.mxd"
MXD = arcpy.mapping.MapDocument("CURRENT")
## Set Data Frame for the layer to select from to the data frame the selected element is in
DF = arcpy.mapping.ListDataFrames(MXD, "Layers")[0] #If the data frame name is not Layers change this
## Pan to selected features
DF.zoomToSelectedFeatures()
## Refresh data farame
arcpy.RefreshActiveView