Your problem is not simple to understand without seeing the phone and not knowing its background.
A lot depends on what problems were with the phone before the firmware was flashed.
If the phone was hanging or working slowly, there may be a hardware problem (oxidation after the water, mechanically bent phone, or eMMC almost dead) after trying to fix it with a software capacitor is not completely flashed. If Odin does not restore, it may be a dead flash drive (eMMC). It's not z3x, it's a phone.
Sometimes in such cases, if the problem is in the software, it can be solved by JTAG. But if the problem with hardware, it is little chance that JTAG will help.
Well, it's unlikely, but it's possible that the moment the phone is flashed, the battery is dead and needs to be recharged.