If folder permission are correct then it should work.
Anyway try this one. And let me know how it goes.
<img src="https://wordpress.stackexchange.com/questions/160273/<?php bloginfo("stylesheet_directory'); ?>/timthumb.php?src=<?php $featured_image_url = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'full' ); echo $featured_image_url[0]; ?>&h=170&w=170&zc=1" alt="<?php echo get_the_title(); ?>" />