Remember when playing Zilean that in lower ELOs there are very few people playing him, this can both be a good and a bad thing, consider your ADC may not know how strong your combo is or when to engage. Equally, your enemy may underestimate you in lane.

Remember in lane that your worst enemy before your first back is your mana pool, Zilean's full combo can be very costly so it is often better to just use one bomb and an auto. Using your bomb rewind and then bomb is a sure fire way to run OOM for a lot of the early laning phase, or worse can force you to have to back early.

With kleptomancy on you can sometimes afford to take a bit of poke damage to ensure you get an auto hit and claim the extra gold, do not do this too much as you will find that Zilean's base health is not that high. gaining extra gold pre level 2 is important as once the enemy laners hit level 2 they will often punish you harder for going our of position for an auto

Mana consumption is a large concern so you will want to be going back once you have earned 850 gold if you find yourself low, if however, you can hold out without spending enough mana then waiting for an extra 150 will provide you with two control wards which will give you much more information on the enemy jungler's pathing when used appropriately

As with any other laner, getting ganked sucks, but with the big fat clock enthusiast you have one trick up your sleeve.

getting ganked whilst you are under tower is going to be great as Zilean as long as you are level 2, at level 2 you will have your slow, your main objective is making sure you slow them as soon as they are under your tower as they will not be able to move out of range without taking a hit. often this is enough to deter the normal jungler as in the early game a tower hit will have a much larger impact. but if they come back for more they will now be softened for you and your ADC to go ham, drop the ignite to prevent a heal from the ADC and make sure that you are dropping those bombs like it is hot.

often in ganks as Zilean you will die, but keeping the enemy slowed in the tower should provide enough free damage for your ADC to kill them, or even better, for you to steal the kill by "accident"