Step 1 Cook spaghetti, according to packet instructions, in a large saucepan of boiling water until al dente. Add green beans for last 2 minutes of cooking time; drain well and return to pan.
Step 2 Meanwhile, slice zucchini into long, thin strands with a spiraliser, stopping at seeds. (Alternatively, grate zucchini coarsely.)
Step 3 Set a large non-stick frying pan over medium heat. Heat olive oil. Add onion; sauté for 5 minutes, or until soft. Add garlic and lemon zest; cook, stirring, for 1 minute, or until mixture is fragrant.
Step 4 Add lentils to pan and stir for 1 minute, or until heated through. Add zucchini strands and cook for 1 minute, or until just bright green. (Do not overcook.)
Step 5 Add lentil mixture to saucepan of cooked pasta and green beans with mint, parsley, feta and lemon juice; toss well to combine.
Step 6 Divide pasta among 4 plates and season with cracked black pepper; garnish with extra mint leaves and serve.