If your trying to get this for your caravel I recommend you just buy 5000 zinc ingots from the market. I had a worker gathering me zinc for a month and only got enough for about 6 upgrade material (artisan 2 processing). it'll cost you just over 100 mil and its the only element of the caravel I consider worth buying from the market. (keep in mind you only need 5k ingots because you can get half the upgrade mats from Ravinca's quest)