It's another cup of tea是英语的一句谚语，一般翻译为“那是另一回事”。

【例句】
Even if you read English easily,you will find it's another cup of tea to make conversation in English.
读懂英语容易，但你会发现用英语对话就是另一回事了。

Even if you read French easily, you''ll find it''s another cup of tea to make conversation in French.
即使你觉得阅读法语不难，你也会发现用法语对话完全是另一回事。