Should I at least be neutral bending towards friendly to the Corsairs/Hessians/BHG there on Gran Canaria to be able to get the Zoner megabribe?
If you have a decent rep with the other factions that offer bribes on GC, it will increase your chances of getting a Zoner triple bribe.
In other words, yes, it helps.
There is a red hessian bribe there, which makes no sense since its primarrily Zoner + Corsair planet.
SPOILER below.
There's at least one more station that offers the mega-bribe...