One thing with the Inkzooka that I've noticed, particularly with more Japanese players lately, is that they seem to be holding ZL as they shoot, basically diving back into their ink the moment after they fire a shot, then immediately pop back out, jump, and fire again, more or less repeated until the special runs out. I'm not sure if that's just an attempt to be more stealthy rather than just standing and firing like a sitting duck, or if that somehow helps to mitigate the weapon's recoil or what, but it's an increasing trend.
I, personally, am dogshit with the inkzooka, just like seemingly every weapon that requires actual aiming, so I try and avoid it on most weapon sets.