If you want to completely customize the thumbnail generation behavior, you can even override theresizefunction. One important point about modifying the size of the thumbnail is that thedz-imageclass provided by the package sets the thumbnail size in the CSS, so you’ll need to modify that accor...
><ahref="<?php the_permalink(); ?>"><divclass="col-sm-6 project-entry"><!--Add thumbnails to potfolio items and resize for responsive--><?php$thumbnail_id = get_post_thumbnail_id();$thumbnail_url = wp_get_attachment_image_src( $thumbnail_id, 'thumbnail-size', true);?><!--...