Not trying to say you don't know, but the more information you give the better your help would be
Knowing what bootloader you have and if unlocked or not will help determine proper steps
Knowing the exact input/output can help as well as knowing the os you are using
Also if tab was working 100% before the attempt to return to stock, prior recovery and rom, any other issues you have had, etc
But its fine if you don't want to post this
Next steps would be
Make sure fastboot binaries on PC are up to date
Quality USB cable
Check md5sum for files you are to flash
If manually flashing stops at sending what happens when you manually erase?
What happens if you just try and boot a recovery through fastboot?
The more info you are willing to give the better your answers will be
Best of luck
Sent from my Nexus 4 using XDA Premium 4 mobile app