I keep reading that people consider Megaroad-01 the SDF-2 Megaroad-01, even in the original Macross franchise (this from the Macross wiki with no Robotech pollution). Further, I read that after SDF-1 Macross, it was decided that having giant ships that transform was impractical, hence the new Megaroad-class ship. Clearly, that's not correct. Then again, the writers may be playing a bit loose with the established canon.
In my blog I question why the Zentradi didn't bother to do a proper planetary survey when they set up a base on this planet. Seriously, as you state, Zentradi military training isn't what it used to be.