1823: three-year-old season

The Duke of Grafton, who bred and owned Zinc

Zinc made her first appearance at the Newmarket Second Spring meeting on 1 May 1823 when she contested the 1000 Guineas over the Ditch Mile course. Despite its name, the race carried a prize of 800 guineas and attracted a field of five fillies. Zinc started the 4/6 favourite and won by half a length from Mr Wyndham's filly Spermaceti,^[4] who had won the more valuable Riddlesworth Stakes at the previous Newmarket meeting. Her victory was the fifth successive 1000 Guineas win for the Duke of Grafton and gave her jockey Frank Buckle the fifth of his six wins in the race.^[5] On the following day Zinc was matched against colts for the first time in the Newmarket Stakes over the same course and distance and finished second, a length behind the 2000 Guineas winner Nicolo.

On 30 May Zinc was moved up in distance to contest the Oaks Stakes over one and a half miles at Epsom. She was made the even-money favourite for the race which carried a first prize of 2,050 guineas. Buckle sent the filly into the lead from the start and despite setting a slow pace she was never headed and held the late challenge^[6] of the Duke of Richmond's grey filly Dandizette "in grand style" to win her second classic by nearly three lengths.^[7] The Oaks was the only occasion on which Zinc raced away from Newmarket.

Zinc returned to Newmarket for the "First October" meeting, which despite its name began on 29 September. On that day she ran in the Grand Duke Michael Stakes, a 1,250 guinea race for three-year-olds over ten furlongs. She started the 10/1 outsider of the four runners and finished second to the Derby winner Emilius, beating both Nicolo and Spermaceti.^[8] At the Second October meeting two weeks later, Zinc ended her season with a win as she again beat Spermaceti and Nicolo in the first year of a £250 Subscription race over ten furlongs.^[9]

1824: four-year-old season

After a year off the course, Zinc returned to action at the Newmarket Second October meeting in 1824. On the first day of the meeting she won 40 guineas for her owner when her opponent, a colt named Don Carlos was withdrawn from a scheduled match race over the Ditch Mile course. A day later, Zinc started 5/4 favourite for the second year of the £250 Subscription race over the two-mile "Ditch In" course and won from the colts Zealot, Premium and Oscar.^[10] At the Newmarket Houghton meeting on 4 November ran a match race in which she was required to carry nine pounds more than Lord Exeter's four-year-old filly Palais Royal. Zinc defeated her opponent over the Ditch Mile to claim a prize of £100.^[11]

1825: five-year-old season

Zinc's first appearance in her final season of competition came on the opening day of the Second Spring meeting when she started favourite for a four runner Sweepstakes over the Ditch Mile. She finished either third or fourth behind the Duke of Grafton's mare Posthuma: at the time it was common for the racecourse judge to place only the first two finishers.^[12]

Zinc did not race again until the autumn. At the first October meeting she finished third behind Stumps and Spermaceti in the Trial Stakes. Two days later she was placed third again behind Mr Bloss's filly Double Entendre in a King's Plate over the three and a half mile Round Course.^[13] At the Second October meeting she was withdrawn from an engagement in an Oatlands Stakes and then ran second to Double Entendre in a ten furlong handicap race, conceding four pounds to the winner.^[14] Zinc's final race came on the opening day of the Houghton meeting when she contested the third year of the £250 Subscription race over the four-mile Beacon Course. She started 4/7 favourite but was beaten by her only opponent, a mare named Black Daphne.^[15]