So, I’m currently having a problem with trying to mirror an object in the Parameters menu.
All of them work just fine, but just type of eyes that I’m using. It works with the Y scale but not with the X scale. I’m thinking because maybe it’s because it’s rotated.
Can anybody help?
[Update] I had to re-import my image with the eye rotated as the default picture.
? Sorry I couldn’t understand.
I currently have eyes with different images using z depth. One of the images in there, I had imported and rotated it in Synfig. (Angry eyes for example.)
If the imported image is a JPEG, check its EXIF Orientation Flag
http://sylvana.net/jpegcrop/exif_orientation.html
Edit: PNG also supports EXIF since 2017
https://ftp-osl.osuosl.org/pub/libpng/documents/pngext-1.5.0.html#C.eXIf
P.S: Why not to use the Switch Layer instead of playing with Z-Depth? 
I’m using a “switch control” using the Z-Depth.