MultiM, Yes a XLR to USB could work for you.
Here are some other lower priced options for you -
ik-multimedia-irig-pre-mic-pre-for-ios-devices
nady-uic-10-usb-interface-cable--10
cme-xcorpio-a-usb-2.0-computer-audio-interface
However, as NecroDM was saying going direct from your Zoom might be the better option. I know you like the sound coming out of your practice amp but since it sounds like your new to recording, I will assume you have not used Cab Impulses...
Your Zoom probably has a Cabinet simulator which may be able to give you some of that natural airy speaker sound that you like coming out of your practice amp. Cab Impulses (IR's) do the same except to my ear are usually much more authentic sounding and give you virtually unlimited options. 1x12,2x12, 4x10, 4x12, and too many combinations of speakers and mics to even begin to list. I would be willing to bet that if you like your tone coming out of a small practice amp, you will absolutely shit yourself when you hear it through an IR. If you are on a budget, you should definitely do some research into these before you buy any additional equipment, and there are an endless number of free ones out there.
Other things to keep in mind, professional and amatuer recordings alike are using multi-tracked guitars, sometimes using differet, amps, ampsims , cabs, mics on each track. And if your recorded tone doesn't sound as heavy and full as you would like, don't forget that the bass guitar and kick drums supply a lot of meat to a heavy sound. Your guitar tone will usually sound way better when it is accompanied by these.
