You could iterate over the repeater field adding the values to an array, then use that array to make the sql statement.
Like:
<?php
$my_sql = array();
// check if the repeater field has rows of data
if( have_rows('repeater_field_name') ):
// loop through the rows of data
while ( have_rows('repeater_field_name') ) : the_row();
//add value to sql array
array_push($my_sql, get_sub_field('zip_code');
endwhile;
else :
// no rows found
endif;
$sql = "SELECT * FROM table_name WHERE field_name IN (".implode(",",$my_sql).")";
?>
