It’s very simply WordPress plugin for „nice“ shows pictures / galleries in lightbox. This plugin implements javascript library fancybox to header and footer pages created in WordPress, functions:
<ul>
<li>you can configure like original fancybox (in admin menu),</li>
<li>you can use multiple galleries on page,</li>
<li>it’s designed for NextGen Gallery.</li>
</ul>

ZMT fancybox

Plugin adds fancybox code to WP header and footer. This plugin is designed for NextGen Gallery. You can use multiple galleries on page.

48hmorris

NextGEN Gallery image upload, image processing, and gallery management functions are moved from the website/browser to a desktop app running on your more powerful desktop system.
Features 
* Super fast image processing – <a href="https://sharp.dimens.io/en/stable/performance/" rel="nofollow ugc">Performance</a> 
* Auto rotate, resize, adjust image quality, create thumbnails, and apply watermarks before uploading images 
* Add/Remove NextGEN galleries 
* Upload images to a NextGEN gallery 
* Remove EXIF data from images 
* Unlimited image file size 
* Secure uploads using JWT Authentication for WP-API Plugin 
* Imposes the same security restrictions as NextGEN Gallery 
* Fast uploads tuned to your WordPress configuration 
* Per-user configuration settings
For more feature details and performance comparisons, visit <a href="https://nextgenassistant.com/" rel="nofollow ugc">Assistant for NextGEN Gallery</a>.
Usage
Once the Assistant for NextGEN Gallery plugin has been installed, 
download and install the companion desktop app (Windows or MACOS) from <a href="https://nextgenassistant.com/" rel="nofollow ugc">Assistant for NextGEN Gallery</a> and start uploading your images.
Requirements 
* Windows 7 (64 bit) or Windows 10 (64 bit) 
* OS X 10.9.5 or higher 
* IIS Web Server – not supported 
* WordPress multi-site – not supported

Assistant for NextGEN Gallery

Save your web server and your time - optimize and upload images, add/delete galleries - all from a Windows or MACOS desktop app.

ZMT fancybox vs Assistant for NextGEN Gallery