Select Sauté on the Instant Potand warm the oil. Add the zucchini, green onions, and thyme and cook, stirring occasionally, until the zucchini are tender, about 5 minutes.
Season with salt and pepper. Transfer the zucchini to a bowl.
Switch to Sauté, add the bacon, and cook, stirring occasionally, until crisp, about 5 minutes. Transfer the bacon to a plate. Spoon out all but 1 tablespoon of the fat from the pot and discard.
Add the onion to the pot and cook, stirring often, until tender, about 3 minutes.
Add the garlic and cook, stirring, for 30 seconds. Add the corncobs, bay, thyme, and water.
Lock the lid in place and turn the valve to Sealing. Press the Keep Warm/Cancel button to reset the program, then press the Manual/Pressure Cook button and set the cook time for 10 minutes at high pressure.
Turn the valve to Venting to manually release the steam, then carefully remove the lid. Discard the corncobs.
Add the potatoes, corn kernels, and half of the bacon and season with salt and pepper.
Lock the lid in place and turn the valve to Sealing. Press the Keep Warm/Cancel button to reset the program, then press the Manual/Pressure Cook button and set the cook time for 4 minutes at high pressure.
Turn the valve to Venting to manually release the steam, then carefully remove the lid. Press the Keep Warm/Cancel button to reset the program, then select Sauté, stir in the cream, milk, cayenne, and zucchini, and heat until hot.
Ladle into individual bowls, garnish with the chives and remaining bacon, season with salt and pepper, and serve.