To craft zinc solder, you need an electrochemical plant... but you can't research the electrochemical plant unless zinc solder is made.

You can handcraft it -w-

Sorry for waiting this long to reply. Yes, I can hand craft zinc solders and zinc rivets but the two researches involving them does not show as complete, as if making them by hand don't count.

https://imgur.com/a/joSeGYv

Never mind, I found a solution. Had to install a "creative mod" to get the researches done. Strange how handcrafting them through that mod worked but not without it.

I do not know whats causing this
Literally no one ever reported this issue