I am able to locate the code in the line you have mentioned in the php file.
But still I do not know what coding should be done at that place in order to display Quiz title instead of course title.
Should I replace the following code :
<?php if (!empty($courseheader)) { ?>
<div id="course-header"><?php echo $courseheader; ?></div>
<?php } ?>
as
<?php echo $quizheader; ?>