Tusk + Zeus

Why this works

Setting up a kill on a single target shows the potential here. Tusk can use Snowball to initiate and then lock a hero down with Walrus PUNCH, giving Zeus a stationary target for his full magical burst. Ice Shards can also trap an enemy, making them an easy target for Lightning Bolt. Perhaps more importantly, a well-timed Snowball can save a caught-out Zeus, who otherwise has no way to escape. This gives Zeus a bit more freedom to position aggressively and apply pressure with his spells during the laning stage and early skirmishes.

The problem is that their game plans tend to diverge as the match goes on. Tusk wants to dive deep into fights, disrupting key targets and applying Tag Team. Zeus wants to stay far on the edge of the fight, safely casting spells and providing global damage with Thundergod's Wrath. Zeus doesn't benefit from Tag Team, and Tusk gets no direct support from Zeus once he's committed. The success of this duo often hinges on whether their early ganks create a big enough lead, because their kits don't naturally build on each other in larger teamfights.