Galaxy S4 active I537 unlock done with Z3X
 

Selected model: I537
Selected port: COM43 SAMSUNG Mobile USB Serial Port
Selected port speed: 115200
Searching ADB device...
Please, allow USB debugging on phone... OK
Reading phone info...
Model: SAMSUNG-SGH-I537
Android version: 4.2.2
Product code: SGH2I537ZBMATT
Phone version: I537UCUAMF3
PDA version: I537UCUAMF3
CSC version: I537ATTAMF3
IMEI: 357365052618168
Phone S/N: R31D90ZFX3D
Checking phone at COM43 OK
Backuping NVM... OK
Checking Super user right... true
Backuping MMCBLK... OK
Writing data to phone... OK
Rebooting phone... OK
Checking phone at COM43 OK
Restoring NVM... OK
Reseting... OK
Unlock done
Done with Samsung Tool v.15.9

Galaxy S4 active I537 unlock done with Z3X
 

Selected model: I537
Selected port: COM496 SAMSUNG Mobile USB Serial Port
Selected port speed: 115200
Searching ADB device...
Please, allow USB debugging on phone... OK
Reading phone info...
Model: SAMSUNG-SGH-I537
Android version: 4.2.2
Product code: SGH-I537ZBAATT
Phone version: I537UCUAMF3
PDA version: I537UCUAMF3
CSC version: I537ATTAMF3
IMEI: 357365050163142
Phone S/N: R31D60RDHMZ
Checking phone at COM496 OK
Backuping NVM... OK
Checking Super user right... true
Backuping MMCBLK... OK
Writing data to phone... OK
Rebooting phone... OK
Checking phone at COM496 OK
Restoring NVM... OK
Reseting... OK
Unlock done
Done with Samsung Tool v.16.0

Oh..Lucky Guys.;)

I Try With Two I9500, Say Unlock Done. But Not Unlocked. :(:(

I Try With One I9505 Say, Reading security... error access denied :(:(