Where is detailed the supporting streng of an assisting unit? In pages 38-39 it is only said that "units with the assist keyword, which usually appears
beneath the unit’s unit summary on the Faction Sheet, (...) are allways supporting units". And the place where appears the assist keyword is, in fact, the place where the other supporting units have its supporting streng.

Thanks you.

They don't add strength to your FLU, so they have no support value. They can't do that because they have no air or ground attack capability. They are always supporting units and needed to play the mighty reinforcement cards they provide.

However, don't forget that you get a +1 bonus on attack if you attack with a Zergling and a Queen or Defiler, and play the reinforcement card #17/#18.

Yes, but that is a rule printed on a card, and cards always beat the rulebook.