First, create a path between the two locations and highlight it, then go to Edit -> Show Elevation Profile (#1).
Right-click the path in the Places tab then click Properties (#2), then click the Altitude tab (#3).
In the drop down menu (#4), if you select "clamped to ground" or "relative to ground" with the box checked for "extend path to ground", you'll ...
BigQuery has a few public datasets, including US counties, that you can directly use.
SELECT geo_id, state_fips_code, county_name, county_geom
WHERE county_name LIKE '%Collin%'
This returns two counties, the one with geo_id = 48085 seems what you need. Here it is in BigQuery GeoViz:
You can change the zoom level of an embedded Google My Maps by adding "&z=X" where X is the zoom, so in your case you would embed your map like so:
<iframe src="https://www.google.com/maps/d/embed?mid=11taTOqfaQSmlryJCcCcwdanSiew&z=10" width="640" height="480"></iframe>
Just change the z=X to whatever zoom you need. Hopefully this helps ...