Steps to Reproduce:

1. Spawn a villager in an enclosed area
2. Place a spawner nearby
3. Use a regular zombie spawn egg on it
4. Wait, and kill regular zombies as they spawn
5. When a zombie villager spawns, open the villager's trading interface

Expected behavior:
When a monster spawner spawns a zombie villager(s), it has no affect on the discounts of nearby villagers.

Observed behavior:
A zombie villager spawned by a monster spawner causes nearby villagers to grant discounts as if the zombie villager had been cured. If the monster spawner spawns a pack of zombie villagers, each additional one causes another discount. Curing one of these zombie villagers causes an additional discount. The discounts are persistent.

For reference, see the following video: https://www.youtube.com/watch?v=sXwk3T_Ay5I

Additional information:
MCPE-91436 reports the fact that monster spawners spawn zombie villagers. Java used to as well, but stopped doing so when zombie villagers were given a separate internal ID. Grum informed us that this behavior (i.e. not spawning zombie villagers) is intentional; see MC-106146. If MCPE-91436 is ever fixed for vanilla parity, this report should probably be closed as Won't Fix.