I don't know their financial circumstances, but its possible that they don't have a spare 500k.
ZC can't do much to fast track a passport, it's not their department. It's also high profile in that if any corners are cut it would not be a good look if someone exposed any shortcuts.
Assume he gets one in due course and he has a bad start to an international career, which is obviously possible, how many games in a row will they give him before they resume their musical chairs of their favorites? That's where we would see some interesting stuff
and some delighted selectors. How many games do you play for Zim before you get offered a starter central contract? Is it based on how well you do or how long they can mess you around- which is practically forever. Once the Big 3 go, who have good contracts based on them being able to squeeze ZC, they can say to the rest- we'll give you 2k a month before tax and not one of them will refuse it.
Those Big 3 have enabled a couple of others to get better deals, but once they retire it's a clean and ugly slate that awaits the others.