Try this one:
Actually, that's strange. It did a full page zoom once when I was in Preview mode, but I can't get it to work again.
I noticed this problem about a few days ago when I went to edit a post that had a pic embedded in a table cell in Medium size. It was now teeny-tiny with no slideshow. Re-embedded it but couldn't get it to show in "Medium" size in the table cell, and it had no slideshow to bring it up in larger size, as it normally did. Finally, moved text out of table format and embedded pic in Medium size, but still no slideshow. All using Rich Text editor.