ibook epub and image resize

It seems to me that it is impossible to resize epub book with ibooks. This isn't a problem with the text but there are images uninterpretable if not larger. This is a problem with tables too. If you have a scientific text this is a big issue.

With pdf files it is possible to resize everything. This is obvious why a text in pdf would be unreadable.

Until now I used stanza and there are no such limitations.

Regards
Gianrico Fichera