爭先〔争-〕 zang¹ sin¹ {zhēng xiān}

1. to compete to be first
2. to contest first place

爭先恐後〔争--后〕 zang¹ sin¹ hung² hau⁶ {zhēng xiān kǒng hòu}

striving to be first and fearing to be last (idiom); outdoing one another