A good way to approach this would be to focus on Voltaire's satirical intentions in the novel. That way, you can identify two literary devices, and analyze the way in which Voltaire uses them to satirize an aspect of society. You can pretty much choose anything about human society here, as Voltaire is mocking everything from war to love to gender roles to materialism to optimism. I'll give you an example using optimism, since attacking that particular philosophy was Voltaire's purpose in writing this text.
- Voltaire satirizes the philosophy of optimism, using juxtaposition and irony in the speeches of the character Pangloss.
Those two literary devices are probably the most common in the text, as the impact of his writing comes primarily from setting up situational and verbal irony. Of course, humor is closely tied to these techniques, creating absurdly funny situations for all the characters. Other devices used include hyperbole and understatement, as well as puns and wordplay.