dual conversion

my magic archer deals lightning and cold damage, and i was wondering.. If i had lets say 65% convert physical to each element, does it just calculate each damage type individually or does that over 50% conflict with each other. it should be obvious i know, but i was reading that conversion happens first and since lightning comes before cold on the scale; would that only leave 35% of the original physical damage to convert to cold.

If you want the full mechanics, I recommend checking out the PoEWiki conversion page:

https://www.poewiki.net/wiki/Damage_conversion

The short answer to your question is:

Conversion that is on the gem "locks in" that conversion. (e.g. a gem that converts 100% of physical to fire can never convert any physical to other elements)

All remaining conversion is scaled to fit the remaining physical damage.

If you have 50% "locked" conversion to fire, then get 100% converted to cold and 100% converted to lightning, you'll get 50% fire, 25% cold, 25% lightning.

Note that "phys as extra" is not conversion, and works separately.

Also note that later steps in the conversion process can still change the "locked in" conversion. So if you have 100% of phys to lightning "locked in", and you have 50% of Lightning to Cold, then you get 50% lightning, 50% cold.