In a large bowl, place lentils, beef, zucchini and egg. Season with salt and pepper. Mix until well combined. Shape into 4 patties. Place on a baking tray. Cover and place in the fridge for 10 minutes to chill.
Spray a barbecue grill or chargrill with oil and heat on medium high. Cook the patties for 4 minutes each side or until lightly charred and cooked through.