Below is the direct link to download the Samsung Z3 SM-Z300H Stock Firmware (flash file) from GoogleDrive. Firmware contains Flash File Only.
Tizen Version: 18.104.22.168
Product code: INS
How to Flash
Step 1: Download and extract firmware on your computer.
Step 2: Download and Extract Odin v3.10.7 or any new version.
Step 3: Open Odin v3.10.7.
Step 4: Now, restart your Phone in Download Mode (by pressing Home + Power + Volume Down buttons together).
Step 5: Now, Connect your Samsung device to the computer and wait until you get a blue sign in Odin.
Step 6: Now, Add the firmware file in Odin using AP / PDA button.
Step 7: Now, Make sure re-partition is NOT ticked before starting the flashing process.
Step 8: Finally, Click on the start button, sit back and wait few minutes to get the flashing process completed.
[*] Take a Backup of your personal data before flashing or installing the firmware on your smartphone. As this helps you to recover the personal data whenever any thing wrong happens.