Indeed, it is good that Zac is home among familiar surroundings and with his pals around him.
If it is concussion, rest and relaxation will do wonders.....I do hope he recovers his faculties soon.
You mentioned earlier that when he sped off into the kitchen, you heard a loud crash and then found him atop the cupboard/unit......I wonder if he got up there at his second attempt, having fallen with a crash and banging his head on the way at the first attempt.
Don't worry too much about the anaemia....that is easily treatable.
Hoping he recovers soon..