Don't worry, you have a few options!
Option One: (I don't have an N7 anymore, so I don't remember if it supports
adb push in TWRP. But I think it does) Boot into TWRP and use
adb to push the file from your computer to your device. You can try to open a Windows CMD prompt or Linux Terminal Emulator, navigate to the local file, then do the following:
adb push AOSP-4.3-JWR66V-grouper-rooted_Androguide.zip /sdcard/
This will push the file to the
/sdcard/ directory - which should exist already (Even on a Nexus device).
Option Two: Boot the device to Fastboot/Bootloader Mode and flash any of the Factory System Images via the fastboot tool. Because using fastboot can be intimidating. You could also use the Nexus 7 Toolkit to automate the process.
This will put stock Android back on your device, and will also remove TWRP. Fortunately, you can use the Toolkit or Fastboot to reinstall TWRP immediately afterward.