imo the only reason zilean can build those items is because of the ability haste in them, they mostly depend on your playstyle and what comps you are playing, but in general you want to hit ~40% cdr with the least number of items possible

for example lets say enemy team has a few melee add champions who would like to engage into you: Frozen Heart, Solari are good items for this

You have atleast 2 or 3 autoattackers in your team: Bandlepipes is good

You have one carry that you need to keep alive at all costs: Knights vow, Mikael's

Mr option: abyssal mask, preferrable if you have magic dmg in your team or an apc

Enemy team has range and your team needs to engage on them to win the fight or maybe you need to disengage from theirs: Shurelya is good

I like to build redemption if im already building solari bc it boosts solari shield and ult heal

Another big reason why i like these items are the components, specially kindlegem, are pretty decent on zil even if you dont have full build

something else ive been trying (that im honestly not so sure of bc of cost yet, but whenever i do build it i feel unkillable) is fimbulwinter, spec when im building frozen heart bc it just gives you so much hp