Theory Crafting on Zilean midlane core build, pls help ^.^

Im a zilean main and I currently build tear -> tier 1 boots/catalyst, but then I thought about how weak it makes his earlygame in terms of lack of cdr. People say to build morello, but in my opinion its a bad item on zilean because zilean needs to be a little bit tanky.

My current idea for earlygame zilean is, prepare for this.... tear -> frozen heart.

Why do I think this works? -20% cdr -mana (works with aa staff by giving damage) -armor (gives good tankiness) -anti-attack speed aura (gives good utility in teamfights)

Why this might be bad -less damage than building roa -no sustain passive from catalyst

Something that is important for zilean is the ability to kill the caster minions with two bombs, but I havent tested frozen heart out yet to see if it would kill.

mini faq: Q: Wouldnt zilean do no damage in teamfights if he doesnt get rod of ages? A: eh, kinda. Its not zilean's job to do damage in fights, he is meant to provide plenty of cc, peel off/catch enemies, and make a 3v3 into a 4v3 with his ulti (the person he ulties pretty much will count as two champs in the early to mid game). Also, his bombs each have 300 base dmg. Q: Why would zilean need to be tanky? A: Its because zilean is able to impact fights not through damage, but instead by cc. If zilean can stay in a fight for a long time, then through the constant cc and slows, he can easily win teamfights.

If you have an idea for core items for zilean, please share your idea ^.^