Scrub the mussels under cold water, discarding any that are cracked or remain open when tapped, and ensure shrimp are peeled and deveined.
In a large skillet with a tight-fitting lid, heat the ghee and olive oil over medium-high heat.
Add the shrimp to the pan in a single layer, seasoning with half of the sea salt and black pepper; sear for 1-2 minutes per side until pink, then remove and set aside.
Lower the heat to medium and add the minced garlic and red pepper flakes, sautéing for 30 seconds until fragrant but not browned.
Pour in the dry white wine to deglaze the pan, scraping up any browned bits from the bottom with a wooden spoon.
Add the mussels to the pan, cover with the lid, and steam for 3-5 minutes until the shells have fully opened.
Remove the lid and discard any mussels that did not open during the steaming process.
Return the shrimp to the pan along with the lemon juice, fresh parsley, and the remaining salt and pepper.
Add the zucchini noodles to the pan and toss gently for 1 minute until they are just warmed through and coated in the glossy garlic sauce.