The author of TruePNG released the new test application - ec-idat (uses for compression of PNG – 7za).
Having carried out a number of tests with different versions 7-zip I revealed essential distinction between versions till 4.32 and after.
7-zip deflate has on much higher proizvoditetlnost than zopfli. About it to the reason it is private it is necessary 7-zip to deflate. I can't resolve an issue of strong dispersion in compression 7-zip deflate in any way.
I would recommend contacting Igor Pavlov (7-zip Author) for advise as change may be resulted of other default settings which can be set by ec-idat program if can be easily recognized.