WordPress.org

Do I need to download HighSlide JS or do somethings on WordPress's theme ?

SlideZoom is Plug & Play plugin. You don't have to do anything at HighSlide JS Script , SlideZoom already hook up the script. And nothing to do about WordPress's theme. After you copy & paste the HTML Code in the textbox and publish the posts, HighSlide's script will load automatically.

What happen if same filename is exist in my images folder? Will it be overwrite?

No, if filename is same, newer file will be append a number as new filename.It apply on both classic file upload or zip upload.

Any foot print ?

The only foot print is SlideZoom need to write one line to WP database's options table , this line named : [slidezoom_options]. If you want keep your wp database clean , simple delete that line after deactivate.

What happen after i deactivate SlideZoom, the images will lost on post/page ?

SlideZoom is 100% flexible! After you deactivate the plugin , the thumbs/images you generated will keep in post/page. And the size will be retain. What you lost is HighSlide effect.

Your english look bad ? Why?

Because i come from HongKong , I speak Chinese :)