Hi,
no, you can't use Template override function for media folder;
templates/{template name}/html/mod_vm_flexible_zoom_effect/media
this is just doesn't make any sense, beside why do you need a template override? and why don't you make your changes directly through;
/modules/mod_vm_flexible_zoom_effect/media ?
For "sizing" the additional pictures we have put some "fixed" element style to thumbnails because otherwise, it has given some unexpected errors (in some websites; slider JS loads before the CSS, couldn't get the proper sizing values and it did lead some weird layout).
To resize the thumbnail follow my steps:
I assume you want to change thumbnails from 70px to (let's say) 150px.
1- open this PHP file:
templates/{template name}/html/com_virtuemart/prouctdetails/default_images.php
2- find this LINE:
<li class="flexible-zoom-additionalImages-slide" style="height:72px; width:72px;">
change it to:
<li class="flexible-zoom-additionalImages-slide" style="height:152px; width:152px;">
3- find this TAG:
..... class="zoom-tiny-image-additional" style="max-height: 70px;max-width: 70px; .....
change it to:
..... class="zoom-tiny-image-additional" style="max-height: 150px;max-width: 150px; .....
and you will be good to go. The additional picture thumbnail will be limited to 150px (maximum in both height and width, which ever comes first.)
Regards.
Forum Support.