Place the oil in a heavy-bottomed pot over high heat.
Once the oil is hot but not quite smoking, add the coriander, cumin, and fennel, and let them fry for about 5 seconds. Add the onions, garlic, and a pinch of salt. Let them sizzle, for about 15 seconds, breaking the onion up with a wooden spoon, then stir in the bell pepper and serrano and let them cook about 10 more seconds. Add the white wine vinegar and turmeric and let the entire mixture come up to a boil. The moment it boils, remove it from the heat and transfer it to a wide bowl. Allow it to cool to room temperature, then transfer it to the fridge to cool completely while you prepare the remaining vegetables and shrimp.
Wipe out the pot (or use a fresh one) and fill it about two-thirds full with water. Season it with salt until it tastes salty like the sea. Bring to a boil over high heat. Meanwhile, set up a bowl of ice water to shock the vegetables.
Once the water is boiling, add the carrots, zucchini, and fennel. Blanch until they are just barely wilted—about 20 seconds. Use a strainer or slotted spoon to transfer them directly into the ice bath.
Cut the lemon in half, squeeze the juice into the boiling water, and add the rinds. Reduce the heat to 190°F, or just below a boil. (If you are working quickly after blanching the vegetables, you can simply turn off the heat and cook with the residual heat.) Add the shrimp and give them a stir. Allow them to poach until just cooked through, about 2 minutes.
Transfer them to the ice bath and then allow the shrimp to just barely chill and stop cooking, about 20 seconds. Lift out the shrimp and vegetables, let them drain, and lay them onto a paper towel-lined plate. Transfer them to the fridge to cool further. Once everything is fully chilled and you are ready to serve, dump the vinegar mixture into a large mixing bowl, along with the shrimp, shocked vegetables, and lime juice. It can be served right away, but for best results allow it to sit, chilled, for 20 minutes. Once chilled, season it to taste with flaky salt, garnish with the fresh herbs, and serve with crusty bread.