Zinc actually helps with hardness. You just add a little more tin to help with full out. Anywhere below 3% zinc you would not even know it's there
That's what I found too. The only problem with zinc I found is storage time.Zinc on bullets oxidizes faster than lead and it can (not necesarly will) make barrel cleaning harder.
If I shoot those bullets within a month of making them whey are better (for my purposes and my powders) than straight WW.