I had an OLD A.R. article on zinc bullets.
They used an undersize .30 mold, then regularly available from Lyman, so as to not have to size down the hard bullets. They melted fresh Zamak die casting zinc in a clean pot.
They loaded the bullets as cast, no sizing, no lube, to full power .30-06.
Accuracy was about as good as hardball, penetration in wood was about like AP, although of course metal penetration wasn't.
Early days of worries about lead pollution on indoor ranges, there was a line of commercial zinc pistol bullets.
Don't use an aluminum mold. The DIY aluminum "welding" process is zinc based.