You're right, Modern seems to have a whole different CSS structure, but the procedure can be refined:
<script type="text/javascript">
$(document).ready(function(){
var zoom = 1.1;
$('*').not('div').each(function(){
var currentFontSize = $(this).css('font-size');
var currentFontSizeNum = parseFloat(currentFontSize, 10);
var newFontSize = currentFontSizeNum*zoom;
$(this).css('font-size', newFontSize);
});
$('p').css('font-size', 80-((zoom-1)*100) '%');
$('strong').css('font-size', '100%');
});
</script>
Put it almost at the bottom of footer.php, just above <?php osc_run_hook('footer'); ?>
Maybe some given element would need individual CSS adjustment,
but this seems to looks fine on main, search and add item pages.
Regards
PS.- There is a really annoying bug in this forum software, plus signs tends to disappear, this line:
$('p').css('font-size', 80-((zoom-1)*
100) '%');
should be:
$('p').css('font-size', 80-((zoom-1)*100)
[plus sign] '%');