Place the shrimp shells, clam juice, 3 c. water, and 1/2 c. of the wine in a 2 1/2-qt. sauce pan. Bring to a boil over high heat. Reduce to low, cover, and simmer slowly for 15 minutes.
Strain the shrimp stock and place in a 4 1/2-qt. sauce pan on the back burner of the stove, adjusting the heat to maintain just below a simmer.
In a 4-qt. chef's pan warm 2 Tbsp. olive oil over medium-high heat. Add the shrimp and cook until they curl slightly, about 2 minutes.
Add 1/4 c. of the wine and reduce by half. Transfer to a bowl.
Add the remaining 2 Tbsp olive oil to the pan. Add the onions and cook until soft, about 7 minutes.
Add the rice and stir to coat the grains with oil, about 3 minutes.
Add the remaining 1/2 c. wine and 1 1/2 Tbsp. of the lemon juice and cook, stirring, until the liquid evaporates, about 1 minute.
Add about 1 cup of warm shrimp stock, stirring the rice constantly. When most of the liquid has been absorbed, add another ladle full of stock and continue to cook until the rice is just beyond the chalky stage, 18 - 22 minutes. If you run out of stock, use hot water.
Remove the pan from the heat; add the shrimp, a ladle of stock, the butter, half the cheese, the lemon zest, and the remaining 1 1/2 Tbsp. lemon juice. Season to taste with salt and pepper. Cover and let stand for 5 minutes.
Remove the cover and stir. Place in serving bowls, sprinkle with the remaining cheese and serve immediately garnished with parsley.