If an IP camera uploads video files, the video files will never be zipped.
If a camera uploads more than 1 images per minute, CameraFTP server will cache these images and save them in one zip file. CameraFTP Viewer apps (mobile viewer apps, web browser-based viewer app and CameraFTP Viewer app for Windows (in Microsoft App Store) can play recorded images/zips like video. There is no need to unzip.
If a camera uploads no more than 1 image per minute, then they will be saved in the original image format.
Your upload frequency is less than 1 image/minute. Most of your files are indeed saved in .jpg format. However, please check in your camera folder (log in to CameraFTP.com, go to My Cameras page, click the folder icon below your camera thumbnail), you can see that sometimes your camera uploaded at much higher frequency (Look at the file create and modify times). It could be a camera configuration problem, please check it; it could also be caused by network issues, e.g. if the camera lost Internet connection for a few hours, and if the camera has internal memory or SD card that can cache images during the time; when the camera reconnects to the Internet, it will quickly upload the cached images.
If you have more questions, please feel free to contact CameraFTP support directly. Note this forum is public. Anybody can read messages here.