Zinc Alloy such as Zamak is formulated to purity standards above "pot metal".
Pot metal is basically whatever scrap gets thrown together and melted (mostly zinc) as used in the 1950s cap pistols or cheap imported "saturday night specials" no standards, slag in the middle, air or corrosion gaps, etc. prone to crack as it aged. Lead in a zinc alloy is a corrosive element over time, and just throwing scrap in a melting pot to make toys, ornaments, etc. gives you alloys that may or may not rot from the inside out.
I would not dismiss all zinc alloy or Zamak as "pot metal". (You can make iron or steel badly for that matter.)
That said, if they made a steel Walter PP or PPK in .22 LR, I would be interested if I didn't already have a .22 Ruger. I just like the old school art deco look (used to have a .32ACP PP almost 50 years ago but couldn't afford to plink centerfire ammo as a teenager).
OK, added: my son has a Walther-made M4 replica with Zamak internal parts (which made part of me go "boo hiss") but with Winchester SuperX it shoots well, is reliable and accurate, and the zamak parts show no signs of wear or stress when I clean it for him every 500 to 1,000 rounds. The chamber must be European match ammo tight, since some "fat" .22 brands won't chamber.