Question:
If a panzer division with an attached Panther (or Panzer IV) battalion suffers losses in combat, is the battalion considered to be a separate unit from the division for loss purposes?

Answer:
Here’s how it works: if a 15-10 panzer division with a 4-2-10 Panther battalion attached is reduced to cadre, the division would count as 19 for loss purposes and you would be left with an 11-8 panzer cadre (a 7-8 panzer cadre with a 4-2-10 Panther battalion attached).

If a 7-8 panzer cadre with a 4-2-10 Panther battalion attached suffers losses in combat, the cadre would count as 11 for loss purposes, and both the 7-8 cadre and the 4-2-10 Panther battalion would enter the replacement pool.

Source:
Errata published at http://www.hmsgrd.com/Files/Europa/Second Front/Second Front.pdf