Suggestion from a diamond level zac top main
Background: I have gotten my accounts to diamond primarily as a zac top for three seasons running. I recently noticed some buffs in pbe for zac. The idea of buffing his elastic slingshot is nice but not what he needs to become more competitive. The range is plenty if you know what you are doing. The big problem for zac is the shadow that appears before he lands. in higher elos, people react to that shadow a long time before you land. I cannot count how many times a thresh flay, Janna tornado or even an alistar ground slam have interrupted my elastic slingshot. Since so much of zacs damage and cc are loaded into his slingshot, it kills his team fight potential. In lower Elos, I can initiate and win a team fight with one well placed elastic slingshot. At higher elos, I am relegated to hiding until the enemy team engages on us and hoping they are too distracted to notice the shadow (which they often do anyway). Changing how that shadow works would help zac immensely in becoming viable again. I would recommend one of two solutions. Either make the shadow visible only when zac is (similar to how fiddle sticks is only scary if you can't see him), or make his shadow grow slowly as he approaches. Increasing the range on his slingshot would be nice, but won't solve zac's core weakness.
-your friendly neighborhood blob