Identify how your recipe uses bell pepper: crunch (raw/quick sauté), sweetness (roasted/braised), or sauce body (blended).
Pick the closest match from the table: roasted red pepper for sweet/smoky softness, zucchini/carrot for quick color, poblano for cooked pepper texture.
Use the 1:1 ratio by weight for even results; for zucchini or carrot, keep pieces smaller to avoid watery or mushy texture.
If your substitute is softer or wetter than bell pepper, reduce added liquid and cook a bit longer to evaporate moisture.
Taste and adjust: add a pinch of sugar for sweetness, or a splash of acid (lemon/vinegar) to brighten the swap.