Zài guānchǎng shàng, yuánhuá de rén wǎngwǎng zǒu de gèng yuǎn.
In the political arena, slick people often get further.
Tips
usage
圆滑 is almost always negative, implying someone is sly and insincere rather than genuinely diplomatic. For positive smoothness/tact, use 圆融 (yuánróng) or 老练 (lǎoliàn).