git archive will accept paths as arguments. All you should need to do is:
git archive -o ../latest.zip some-commit $(git diff --name-only earlier-commit some-commit)
or if you have files with spaces (or other special characters) in them, use xargs:
git diff --name-only earlier-commit some-commit | xargs -d'\n' git archive -o ../latest.zip some-commit
If you don't have xargs properly installed, you could cook up an alternative:
#!/bin/bash
IFS=$'\n'
files=($(git diff --name-only earlier-commit some-commit))
git archive -o ../latest.zip some-commit "${files[@]}"
Written as a shell script, but should work as a one-liner too. Alternatively, change earlier-commit, some-commit, and ../latest.zip to $1 $2 and $3 and you've got yourself a reusable script.