Place the spaghetti in a large pan of boiling water and simmer for 10-13 minutes - until cooked to your liking. Note - you'll be adding the sugar snap peas and courgette to the spaghetti for the last minute of cooking.Whilst the spaghetti is cooking, heat the oil and butter in a large frying pan (it needs to be large enough to hold the cooked pasta later).Sprinkle a pinch of salt and pepper on the salmon fillets and place in the frying pan skin side down. Cook for 3 minutes, until the skin is crispy. Turn the salmon over and add the onions to the pan. Cook the salmon and onions for a further 3 minutes, until the onions start to soften.Take the salmon out of the pan and place on a chopping board.Add the garlic to the onions and cook for a minute whilst stirring. Add the wine and let it bubble for a minute, then add in the cream. Heat through slowly.Whilst the cream is heating through, remove the skin from the salmon, and break the salmon into rough chunks (don't worry if it's not quite cooked at this point as it's going back in the pan). Add the salmon back into the pan with the cream. Also, add the lemon zest.By now the spaghetti should be almost ready. Add the sugar snap peas and spiralized courgette in with the spaghetti for the last minute of cooking.Drain the pasta, reserving about half a cup of the cooking water. Add the spaghetti, sugar snaps and courgette to the frying pan and toss through along with a good splash of the spaghetti water and the lemon juice.Divide between four bowls and top with grated parmesan, freshly ground black pepper and a little bit of lemon zest. Serve with lemon wedges.