I dont own a cruz but do have 4 other tablets and the 2 main methods i use to load apk's are this
1) if its iin a zip file, extract it on your PC to its basic XXX.APK format, the less work you ask the tablet to do the happier you'll be. once you have your APK file the 2 methods i use to get it onto the device are this:
1) on my XP and Linux PC's I have downloaded the android SDK, i plug my tablet into the usb port and then use ADB from the tools submenu on the pc to install or push the APK to the tablet.
2) the simpler method, but does rely on the dvice being 'rooted', is to pop out the micro sd card from my tab pop it into,y pc reader and copy the file to the carrd, then put the card back into the device and install from there.
the 1 method that i always think SHOULD work that never does, is to email the APK to my gmail account and then downlload the file onto my tablet from gmail. somethiing in that process always corrupts the file.
if any of these terms are unfamilar do a search through the forums and you should find exact definitions and how tos
2 other forums that helped me learn a LOT are slatedroid.org and xda-developers.org
xda is a very technical forum but ifit can be done on a tab THEY have done it.
hope this helps