can you do lead 1 time then zinc at another time with same eqpt. without worry about contamination from the opposite metal you are working with? and is zinc and lead weighed the same 1=1? say using your aluminum mold with lead is 220 gr and the same weight as with zinc?
The molds have no issue being used for both lead or Zinc. Your pot has to be cast iron! Your molds should be steel! Zinc will eat thru standard casting pots. No one makes an affordable cast iron bottom pout pot. The pot I have is a Saeco #24 cast iron pot made back in the 60's - Lyman also had the same pot was a Lyman 61 pot. I found mine on ebay. Took me months to win a bid on one. The prices were all very high for something that might not work. Replacement parts are not available. You can get parts that you have to adapt. A thermostat is available for $40 but the coil you have to buy a straight coil and manually bend it to make a replacement which takes some doing. I did use an aluminum mold to play with which worked but over a short period of time you would damage the mold. The 230 gn lead bullet mold casted 138gn Zinc bullet. You have to work up a load as there is no load data for zinc. But with that porgram Quick loads you can get load data to work with.