if the scouts are positioned behind the artillery but out of intermingled distance, you can engage the artillery and effectively ignore the scouts, this is covered in the FAQ:
Quote:
Q: It’s possible to place a Scout unit
just behind another friendly unit, so
that the Scouts 10cm ZOC covers the
friendly unit too. If this happens, can I
charge the non-Scout unit? The rules
say I can’t enter a ZOC unless I’m
charging the unit it belongs to.
A: You are, of course, allowed to charge
the unit! If an explanation is needed, then
let’s say that the rule for moving into base
contact with the enemy takes precedence
over the rule for not entering another
unit’s ZOC. However, any player who has
attempted to use this tactic to stop a
charge should hang their head in shame!
if however you wish to engage the scouts, provided you can reach them to FF without entering the artillery ZoC then you can engage them, however you can't enter the ZoC of the artillery to engage the scouts as you may only enter ZoC if you are engaging the unit that owns that ZoC