You can import PNG, JPG, or GIF files as screens into a project from Zeplin’s Windows and Mac apps. To do this, go into the project that you want to import the images into and select the “Edit > Import PNG, JPG or GIF…” option from the desktop menu up top.
Choose the image files you'd like to import, then click the “Open” button. The images will be uploaded to your project as screens, without any layer details.
☝️ Since this is an image not exported via the plugin, it will not contain any technical resources like layers, assets, and code snippets for screens imported as PNGs. To export the screens with their technical resources, you need to export them directly from the design tools through the plugins.