Gzip encoding has been part of the HTTP protocol for a long time and every server-side HTTP library out there supports it, and phishing/scrapper bots will be done with server-side libraries, not using browser engines.

Further, judging by the guy's example in his article he's not using gzip with maximum compression when generating the zip bomb files: he needs to add -9 to the gzip command line to get the best compression (but it will be slower). (I tested this and it made no difference at all).