Combine the pistachios and oil in the work bowl of a food processor. Blitz until the nuts are finely ground, about 30 seconds. Add the feta, cilantro, dill, ⅓ cup of the yogurt, lemon zest and juice, and chili. Process until well combined with a pleasing coarse texture, stopping occasionally to scrape down the sides of the work bowl, about 1 minute. Thin with additional yogurt, if desiared. Season to taste with salt if needed (feta is salty, so you might not need any additional salt). Serve right away, or cover and chill up to 3 days. If chilled, let stand at room temperature at least 30 minutes before serving.