Turning villagers into Zombies

I have looked around and don't really seem to be able to find reliable info on what is going on, or at least not all in one place.

I have noticed during my attempts to make a villager breeder to profession selector to zombificator to cured villager to trading hall build that I run into a consistent problem.

The damn zombie seems to straight out murder my villagers much more often then zombificate them. I estimate between 60-80% of the time the villagers die.

I am on normal difficulty. I have tried villagers in a boat, villagers in mine carts in an out of water, villagers on a piston with trapdoor, zombies held back by string, held back by trap door....

I tried a zombie with a non damaging item in their hand, a zombie with a sharpness V iron sword, a diamond sword, dropping the villagers a distance first

To account for the regen I tried zombificating them before trading, directly after trading, directly after leveling up their trading... I had mild success with leveling them up and then letting them sit then trying but my stupid machine for doing that kept breaking and letting the villager into the zombie area or out into the open so i didn't get as many tests with it to see if it was the same as the other.

So what is going on? Is there an agreed upon stage of the process where the villager is most likely to turn into a zombie? Does it effect the chances if the zombie has better damage or worse damage? What the heck is going on with all my villagers being murdered instead of turned into monsters so I can "rescue" them?

I have begun to hate villagers, I feel a small, red hot ball of fury developing deep in my soul towards these frustrating bastards.