Hi sorry I've sort of fallen off the modding train for the past several months but I think the worst of the Impending Life Events are past now (knock on wood).
I have zinc and nickel generating at about half the overall amount as iron (but it's complicated). For a vanilla game this is about right for nickel and probably a bit too much for zinc. I'm not super familiar with how K2/SE + vBZ mods goes and all my intuitions for this are based around the base game, so for instance messing with how many iron plates are needed for steel like Krastorio does is going to throw the ratio off.
Zinc is universally needed less than copper since the two things that use it by default (brass and batteries) use equal amounts of zinc and copper but copper is still needed in all the usual places. (not true of batteries if you have both lead and nickel but batteries are also pretty marginal in terms of how much of your total resource usage they represent.) If you're decreasing the copper yield to compensate for BZ mods decreasing the amount of copper in electronics, consider reducing it by less with BT since brass is needed for things like gears that don't normally need copper at all. Extra intermediates adds a couple recipes that need zinc without copper but they aren't needed in nearly the numbers that brass or copper are so they don't really cancel out the general rule.
Nickel has higher base_density with AAI because the AAI electric motors are significantly more expensive than my motors and I wanted to keep the resource ratio about the same. Extra nickel intermediates mostly just stuff more motors into things, at which point it's probably closer to 60-75% of iron especially if you factor in other iron being replaced in recipes. But nickel is generally more heavily needed for infrastructure than for science, especially with K2, so it depends on what general sort of factory activity you're basing the ratios around.
