Messages: How do I get videos to play full-screen?

Videos I receive in Messages can't be zoomed to full-screen in iOS 8.3. At least, I can't figure out how to do it. Both iPhone and iPad...same thing. Pictures, no problem...just double-tap.

For videos, you need to save to your camera roll and then go into photos which is ridiculous. Is there a way to do full-screen videos from witching Messages?

Regards, Patrick