Help!!!!

Eathan is 6 yo and has started throwing temper tantrums like he's Jacobs age which is 2 yo. Eathan is the middle child so I'm not really sure if this is part if that middle child syndrome I've heard about or just another phase but I'm at the end of my patience rope. Especially now that he's throwing toys and slamming his bedroom door. I've tried everything and now I'm asking for help or any new ideas to try out.