pictures show twice in android app

Question

I received a 250MB epub file and unzipped it (with 7z) and just recompress it's jpeg's to ~50% size (not dimensions), keeping the same files names (with IfranView).

I reziped to .epub and loaded it to my android tabs. Two apps open it but will display each picture twice. Once without adjacent text and the second time with text I do not have any special epub authoring software.

Why it happened and can I correct it?

Answer 1

After so long I came back to this issue and found the solution.

1. I open the epub in 7z (but not unzip)
2. I drag the image folder out and recompress it with Ifranview to my liking.
3. Now I drag it back into the open 7z window to replace the old image folder close 7z, and now the epub is half size and opens correctly in any epub app,