OK, it's clear to me now that the size is the correct one. It was not my intention to blame Yamato, in fact, I own several figures from them and think they're the best around.
Anyway, you have to admit that Zentraedis are equal in size to valks: remember the first encounter (Hikaru defending Macross island), the fight with Britai, the scape (Max covers his valk with a "standard" soldier's suit), and so on. Miria here is the exception that confirms the rule! I know, I know ... "check the specs for the correct sizes...", but I was referring to what is seen in the TV series ...
Regards everybody!