- Sharma wanted the money that Zac represented he had.
- Sharma remarked to Shamji (before the events) that Zac, having involved himself with them, was not allowed to run away.
- Zac was thinking (before the events) of entering witness protection.
All indications are that nothing special happened that night; the situation had already gone bad. Why postulate a comedy of errors?
- The "hint of a Russian accent" that Zac supposedly put on (but nobody except Shamji ever noticed)
- How quickly Shamji and his associates were to claim that Zac "seemed suicidal"
- The "heating up knives and clearing up blood" text from Shamji hours before Zac's death
- The traces of blood spotted by the police when they searched the apartment Zac jumped from
But hey, the cops asked a few questions and none of these shady characters instantly signed a confession so what more could they possibly do?
It's already known that they knew he jumped into the river; this is pretty easy to explain.