Both Zone Alarm Internet Security, and Zone Alarm Extreme Security (the paid for suites, NOT the free firewall) disable Defender, as it has it's own Anti-Spyware (Assuming your using the full suite of course)
I'll echo Borg's comment's though, I am a long time ZA user and fan, and had to ditch it with 7 after numerous unexplained BSOD's which seemed to point to a corrupted HDD. Turned out that ZA was ripping up the file system everytime it scanned. Coincidentally my ZA was also for some reason not stealthing ports, and when I uninstalled it, the BSOD's went away. 3 months I spent trying to figure that out
Of course this was back when 7 was still new, so thing's might have changed since then, but "once bitten, twice shy" and all that.