Heat oil in medium skillet over medium-high heat. Add onions, garlic and jalapeno and cook, stirring frequently, for three minutes or until onion is translucent. Stir in curry powder, cumin, coriander and turmeric. Cook, stirring constantly, for one minute. Scrape mixture into the slow cooker.
Add tomatoes, lentils, stock, cinnamon sticks and cardamom pods to the slow cooker. Cook on low for three to five hours or on high for 1 1/2 to two hours or until lentils are almost soft.
While lentils are cooking, preheat the oven to 350 degrees. Toast cashew nuts in a single layer on a baking sheet for 5 to 7 minutes or until lightly browned. Set aside.
If cooking on low, raise the heat to high. Remove and discard cinnamon sticks and cardamom pods, and add zucchini and cilantro to the slow cooker. Cook for 30 to 45 minutes or until zucchini is tender. Season with salt and pepper, and serve immediately over rice.