Final answer:
Lily's tears with Zach likely result from a mix of emotions, whether due to personal reflection, romance, or sorrow. Specific details about their situation are needed for a precise reason, but crying is a common literary tool to convey profound emotional states.
Step-by-step explanation:
Lily breaks down crying with Zach likely due to a burst of emotions related to past events, memories, or strains in her current situation. Characters in literature often cry as a response to moments of intense feeling or an overwhelming sense of nostalgia.
For instance, emotions can surface when confronted with the mortality of loved ones, like Hagrid's tears for Lily and James in 'Harry Potter'. Alternatively, crying can be a character's reaction to a romantic situation going awry or a reflection of their deeper emotional state, as observed in the excerpts about Judy and Kismine.
Without more specific context about Lily and Zach's situation from the question, it is difficult to pinpoint the exact reason for Lily's tears. However, it is common for characters to express a wide range of feelings including sadness, frustration, fear, helplessness, or joy through tears.