render differences from pocketbook reader

[eberna]

Dear all,
Before posting this message i tried to find a solution searching online and experimenting all render settings in the document without success.
I own a pocketbook inkpad color 3 and i would prefer to use the koreader reader instead of the integrated one. I an trying to read an IT book from OReilly in epub format and the render in the integrated reader in much better. How could i improve the render in koreader to match the results?
Many thanks for the suggestions.
Here an example with koreader

And here the pocketbook integrated reader

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