
Samsung Z4
The latest firmware for Samsung Z4 (SM-Z400F) is Z400FDDU0BRB1 with Android 3.0.0.1, released on February 27, 2018 for 1 region (CSC). Every official firmware build for SM-Z400F, newest first: one row per build with all regions (CSC) that received it.
Each firmware build has its own page at https://samfirm.shop/build/{PDA}, where {PDA} is the build number from the list above. Example: https://samfirm.shop/build/Z400FDDU0BRB1
All 6 builds in our database run Android 3.0.0.1. The newest build, Z400FDDU0BRB1, was released on February 27, 2018. No new build has appeared for 105 months, so regular updates for this model have most likely ended.

SM-Z400Y

SM-Z300H

SM-Z200M

SM-Z130H
The newest firmware for SM-Z400F runs Android 3.0.0.1: build Z400FDDU0BRB1, released on February 27, 2018.
The latest build for SM-Z400F, Z400FDDU0BRB1, was released on February 27, 2018 (8 years ago).
SM-Z400F has had no new firmware for 105 months, so regular updates have most likely ended.
Yes, all firmware files for SM-Z400F are 100% official, original, and obtained directly from Samsung servers.
To flash SM-Z400F, you need to download the appropriate firmware, put your device into Download Mode, and use the Odin tool to load the BL, AP, CP, and CSC files.
Downgrading is only possible if the bootloader version (binary bit) of the old firmware matches the current one. Always check the binary version before flashing SM-Z400F.