couple of thisngs when working with multiple selects;
the select list name must end with  to create an array of the selections:
<select name="zipsCover" size="8" multiple id="zipsCover">
you will need to modify the insert record code to use the php implode function on the zipsCover element.
there will be code similar to:
this will need to be changed to:
GetSQLValueString(implode(", ", $_POST['zipsCover']), "text")
this will convert the array of selections to a comma separated list.