What I expected to happen was... 

Zombies can always see the villagers no matter the villagers are in a house or any area.

What actually happened was...

Zombies are unable to see the villagers if the villagers are in a house or behind a wall.

Before version 1.14, zombies would able to see villagers through houses or walls, but after the Village & Pillage update, this feature is no longer works, the zombie's behavior seems broken, and this change is not listed in the changelog.

Since zombies are no longer able to see villagers through walls, they now requires to breaking doors by random pathfinding if they has CanBreakDoors NBT tag, but they usually fails when tries to break doors by random pathfinding (they just trying to break the door a few times, then give up breaking the doors and walk away). So the zombies can only reach and see the villager if the house's door is not closed, and I did not see anything about the behavior being removed when I looked on the wiki, and the wiki still describing this point. (see the attached image below). 

I found that this issue is not present in the Bedrock Edition, possibly classifying things as a parity issue because it's not Bedrock exclusive.

Relates to MC-148379.