In a large mixing bowl, combine all-purpose flour, baking powder, cornstarch, and salt to form a dry mixture. Gradually add water while stirring until you achieve a thick batter with a smooth consistency, ensuring there are no lumps. Set aside.

Add the sliced zucchini, sweet potato, shredded carrot, sliced onion, and chopped scallions to the batter, folding gently until all the vegetables are evenly coated. If desired, add optional green chili or jalapeño.

In a small bowl, whisk together soy sauce, water, vinegar, sugar, and sesame oil until well combined. Adjust seasoning to your liking. Set aside.

Heat a non-stick frying pan over medium-high heat, add neutral oil. Pour in a ladleful of batter, spreading to form a thin round pancake. Cook for about 4-5 minutes until edges crisp and underside is golden brown.

Carefully flip the pancake and cook the other side until golden and crisp, about 3-4 minutes. Repeat with remaining batter, adding oil as necessary.

Remove pancakes and let drain on paper towels. Cut into bite-sized pieces and serve warm with dipping sauce.