another excellent tip:

if they are melee,  like talon, kass, pantheon, alkali, diana, j4, jax, etc., bomb your ally minion before they CS it. I find that NOT smartcasting this Q is more effective and reliable than smartcasting.  If they don't CS it but are still near the bomb (or walking towards you), you can bomb it again to make the first one explode and still hit them with at least one bomb. This effectively extends the range of your bomb by the radius of the AOE. If the minion dies quickly after u bomb it u might still hit them with both bombs. It's like playing a different kind of mini-game within the laning phase. 

Another  IDEA for team fighting: stay with your ADC, possible behind or to the side of your ADC. Use your ult like a type of "Peel" for the ADC when they get focused. Put a bomb on your initiator and let them run in with it or stay with ur adc and slow and double bomb whoever dives your adc. 

If you try that stunt on Akali, Jax etc, they will jump you.

jax jump is range 700, the same as zilean. U definitely need to watch out for it especially later on, but early, he's trying to last hit. 

also zilean ideally positions himself so he is just in range to bomb the minion but not jax, thus keeping you out of range of jax's jump. 

if jax stands between you and the minion, then u have to bomb jax instead. if he does jump to you early, now he is behind your minion lines so u can slow him as all your minions turn to hit him. as he walks away bomb him again. i definitely need more practice with the execution of it but thats my idea for how to play against jax mid lane, if you dont think it will work can u be more specific as to why not and suggest a better way to approach it instead?

as for akali, her Q range is 600. Her ult range is 800, so she can certainly jump on me, but not before level 6! so remember the context of the idea i was giving, maybe i didn't make it clear, is pre-6 laning strategy to harass safely against melee gapcloser mids. Pre-6 i bomb her a lot, on her directly or her CS, after a couple of these she usually gives up and just farms with Q instead. If she shrouds near a enemy caster minion, ideally i double bomb it and hit her with the AOE. my problem against akali and other weak pre-6 laners is their 9 hp pot start or whatever it is. They just outsustain my mana pool despite me starting 2 faerie charms,3 hp pots, and clarity/ignite, with scaling mana regen yellows. maybe i should try switching back to flat mana regen yellows. I'm really looking forward to this max 5 hp pot change. The other problem is i don't run flash, so i'm really paranoid about getting ganked and don't like to push the lane without wards at all, which makes it hard to all-out harass early.

Another idea i have for akali that i haven't tested much yet is to wait for her to use spells and go on CD, then she shrouds, so then bomb urself and walk into the shroud. since her spells are on CD, she has 2 choices, stay in the shroud and the bomb on my head will go off and hit her, or leave the shroud, then i can see her and put a bomb on her head that way as well. This is a pre-lvl6 idea only of course.

are you a fan of zilean or not? i can't tell. Are you here to discuss how to play zilean better or just dump on him, or trying to learn how to play against zilean? either way, thanks for your thoughts i hope to have more conversation with you. Hey, would you be interested in some 1v1 practice matches to test it out?

my summoner name is chronoshifter and im the biggest ZILEAN fan!

I am a fan of Zilean support, but I never solo lane with him. Whenever I use him against aggressive gap closer champions as you described, it has resulted in many deaths. An issue with his time bomb (I have never experienced it, but I would expect trouble) is that it can be dispelled through a QSS. Accurate minion bombing is fairly difficult due to the fact an enemy has four seconds to escape the area unless you are really good at predicting which minion they plan to last hit. 

Obviously, pre level 6 you will have a huge advantage, because you get your main damage source at level 1, and most chapions have high damage ultimates. The issue I think of is middle game, where you don't have layers of AP on yourself, and enemies have QSS for your slow bomb.

"Whenever I use him against aggressive gap closer champions as you described, it has resulted in many deaths."

i agree, this used to be really hard for me as well. 1 tip: don't engage them without ur ultimate up. Have a friend pick one of these champs ur having trouble with and do some practice 1v1's. Once you get out of that valley, it is so green on the other side! I love facing a talon or kassadin now. Love it! I really encourage you to keep playing the difficult matchup "counters". I used to have so much trouble with them but now i love to face them. I used to have trouble vs gragas as well. Now i play less aggressive against him, stand away from minions so he must choose between Q harassing me and Q for CS and do so much better. What i love about Zilean is i feel he is so deep a character, depending on the matchup i use a different laning style / strategy, the trick is just to figure that out. 

I admit i still do have a really tough time now vs master yi (out-sustains me, easy to harass me with Q) , soraka (silence + sustain), and elise (rappel to dodge bombs or gap closer onto me)

"An issue with his time bomb (I have never experienced it, but I would expect trouble) is that it can be dispelled through a QSS"

why is it an issue if you have never experienced it?

i have never experienced people using QSS to dodge a bomb either. However i have seen plenty of bombs negated by abilities such as vladimir going underground, Fizz trickster, Im guessing Lissandra's R / Zhonya's will also dodge the bomb, and Elise Rappel as well. And there are many champs with strong shileds like morgana, oriana, jarvan, lux. Doesn't dodge the bomb but hurts a lot less. As for items, i have seen people buy the Hexdrinker item or elixir of fortitude to live thru a bomb as well. So for those reasons, yes, i agree it is an disadvantage. 

So Zilean's Time Bomb isn't perfect! So what? Again, I don't play him b/c i think he is OP or the best, i play him cuz i love him, he is not popular,  and want to maximize his potential. I don't want to solo lane using the most OP champ. 

BTW i think this 5 hp pot is a great buff for zilean!

zilean jungle is broken ;~;

ALWAYS GET W FIRST

I used to do that, but then they nerfed him so you can't get it first nymore :( ;)

I found an other good counter for him, kha zix. before you can cast him slow... he is next to you and burst such a lot dmg on you

I know it's anecdotal, but I haven't found Kha problematic.  He has a strong initiate, but I just hit myself with an E and I'm safely behind the turret.  That and I found it pretty easy to deny farm :)

how about lichbane?

slower burst but much higher DPS

just an idea as a 6th item instead of zhonya's perhaps

o wait nvm it only trigger on spell damage right? not just by casting a spell. 

nvm bad idea!

It procs after casting any spell, so you can cast a slow, autoattack, bomb autoattack, rewind, autoattack, then bomb again autoattack. But think really carefully, do you really want to autoattack someone with Zilean?

How about dfg? So the bomb aren't his only source of damage.