How many actions can a summoned zombie use?

Many zombies – such as the Zombie Shambler – are permanently slowed 1, which reduces the number of actions they can use by 1 each round. Summoning such a zombie with a spell (such as Animate Dead) gives the zombie the summoned trait. This makes the creature a minion with only 2 actions that it can use per round.

Since the zombie is permanently slowed 1 and starts with 2 actions, one would be led to believe that such a minion could only use 1 action per round. However the summoned trait has this clause that casts some doubt on that assumption:

Immediately when you finish Casting the Spell, the summoned creature uses its 2 actions for that turn.

Does this grant the newly-summoned zombie a second action to use? If so, is it for that turn only, or for the duration of the summoning?