
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Let $Z_1 = a + bi$ and $Z_2 = c + di$, determine the condition for the complex number $Z_1 \cdot Z_2$ to be a real number.

Present the answer in LaTex format: \boxed{Your answer}
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