Preheat the air fryer to 390°F (200°C) for 3–5 minutes.
Wash and trim zucchinis; halve each lengthwise and pat dry with paper towels.
In a bowl, toss zucchini halves with olive oil, garlic powder, salt, pepper, and paprika until evenly coated.
Arrange zucchini cut-side up in a single layer in the air fryer basket (do not overlap).
Cook at 390°F (200°C) for 6 minutes, then check for browning on the edges.
Flip zucchini halves gently if you want even browning, or leave cut-side up for a tender interior with crisp edges.
Continue cooking another 3–6 minutes until edges are golden and flesh is tender when pierced.
If using Parmesan, sprinkle it over zucchini during the last 1–2 minutes to melt and brown slightly.
Remove zucchini to a serving plate and drizzle with lemon zest or a squeeze of lemon.
Garnish with fresh thyme or parsley and serve immediately for best texture and flavor.