eBook Publisher

I need help please, I can't find it anywhere.....

I am using ‘Publish to eBook’  in ‘eBook Publisher’ (that comes with Corel WordPerfect) to create EPUB. I noticed that in eReaders when I zoom images ( just a little) they become foggy, not clear & sharp. Then I found that in EPUB dimentions of images have been reduced, e.g. images with Width 1250 pixels are now with Width 728 pixels. Also in EPUB all images have been converted from PNG to GIF. How can I tell the software not to reduce the dimentions of the images, and not to convert the images?

Thanks a lot