Is “Is Zheng Anping not yet recorded in historical records, and only described in novels as helping Fan Ju flee to Qin, later serving as a Qin general, surrendering to Wei, and causing his entire family to be executed?” true?

The candidate document's claim that 'the histories have yet to record him' is wrong -- and that phrase is the candidate list's own assertion, not a quotation from any classical text. The 'Records of the Grand Historian, Biographies of Fan Ju and Cai Ze' records Zheng Anping clearly: as a man of Wei he helped Fan Ju escape -- 'Zheng Anping of Wei heard of it and thereupon carried Fan Ju away in flight; they went into hiding, and he changed his name to Zhang Lu' -- and was later made a general on Fan Ju's recommendation: 'He appointed Zheng Anping to attack Zhao. Zheng Anping was surrounded by Zhao, and in extremity surrendered with twenty thousand men. The Marquis of Ying [Fan Ju] lay on straw to beg punishment.' The novel has him surrender to Wei rather than Zhao, and the execution of his family is an extrapolation from Qin's collective punishment law. He is by no means a fictional figure absent from the histories.