Thargoids aside, because I wouldn't know, CZs are the hardest form of PvE combat. Enemies are at least fully A-rated, smaller ships are proper hull tanked and bigger ships are shield AND hull-tanked.
If you have the credits (22m), buy a Vulture and build it like
THIS. I'd need to see video evidence that a Cobra can last long enough in even a Low CZ to get more than one kill, with minimal experience and/or no more engineering than this Vulture build. Don't discredit the Multicannons, they are perfectly fine for this method. You'll need the 5A shields (not bi-weaves, the Vulture doesn't make use of quick recharge). You don't need heavy weapons for this: read on.
Before entering the CZ, make sure you have buttons mapped to quickly activate shield cell bank AND heat sink. Make sure you have multicannons set to primary fire and chaff to secondary, then arrange your pips as per the above link.
Now, enter any Low CZ, move to about 6km from the fighting, stop. Wait a few seconds for the inevitable handful of extra ships that will drop in. THEN choose your side - making sure the enemy isn't the controlling faction of the nearest station. THEN - would be best to map to buttons/keys - scroll through enemy ships using 'Cycle next hostile target'. Keep scrolling until you find one with no shields, head quickly for that enemy, ignoring any fire you take for now. Make sure your ally is still firing on the enemy ship, wait for the hull to drop to maybe 15% for smaller ships, under 10% for biggest ships, and start firing. The enemy won't last long so if they decide to turn their weapons on you quickly they won't have time to do too much damage. Repeat, find enemy with no shields, wait for low hull %, finish them off. As long as you hit them with at least one bullet before their hull reaches 0% you'll get the kill.
Watch your shields (you may have picked up a tail on your boost to the shield-less enemy) and if you face heavy fire from an enemy pop chaff and a shield cell bank (and heat sink at the same time!) straight away. Even if your shields are full, the cell bank takes a few seconds to activate and by then you could very well have lost a ring or two.
UNDER HEAVY FIRE = chaff, boost, shield cell/heat sink, full throttle, second chaff, boost, boost, boost. The enemy will usually give up the chase once you're 10km away.
One kill = one combat voucher. You can claim bounty vouchers in the same system the Low CZ is in, it doesn't matter who owns the station, including if the enemy owns it. If you run out of ammo or cell banks, simply boost out of the fighting zone and low wake to the nearest station for re-arm/repair where you can claim the vouchers you've earned so far, at the same time.
Good luck.