Heat oil in a wide cast iron or heavy skillet over the highest heat possible until smoking. Add zucchini rounds in a single layer, working in batches. Press down gently for full contact. Sear completely undisturbed 2-3 minutes until the underside is deep golden and caramelized. Flip once and sear 1-2 more minutes. The rounds should have a hard golden char on both flat faces with the green ring clearly visible at the edges.
Dress
Pour garlic, chili crisp, soy sauce, rice vinegar, sesame oil, and sugar directly over the zucchini in the pan. Toss until every round is evenly coated. The residual heat will bloom the garlic and help the dressing soak into the surface.
Plate
Arrange zucchini rounds on a plate. Finish with sesame seeds and scallions.
Notes
Don't move the zucchini while searing. Let it release naturally or it tears.
Dress while hot so the residual heat blooms the garlic and helps it soak into the surface.