Gǎnxiè gèwèi tóngrén duōniánlái de zhīchí yǔ hézuò.
Thank you to all colleagues for your support and cooperation over the years.
Tips
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同仁 is more formal than 同事 (colleague). It often appears in official speeches, written communications, and names of organizations (e.g., 同仁堂, a famous traditional medicine company).