Zilean's passive should give assists
I was in a game where I as support Zilean and my adc who was Lucian were pushing the enemy laners under turret. My Lucian was level 5 and my passive came up. I put my passive on to him which gave him level 6. Immediately, Lucian levels up his ult and gets a kill on the enemy ADC under turret.
I did not get an assist. What the hell? Felt bad. :(