The most meaningful way to conceptualize cancer, IMHO, is as "evolution on the cellular level".
This is why it is so hard to beat: A cancer may begin as a single (or small number) of mutations. Cancers start all the time and our immune systems usually wipe them out in short order. But past a certain critical point a cancer develops a tendency to change rapidly (by a varieity of mechanisms, some more powerful than others) and that is the point where it really becomes deadly. The difference between a "benign" cancer and a malignant one is often a matter of the latter having powerful tools for genetic variation the former lacks.
Evolution is by a massive margin the most powerful "force" in nature (life is present in every nook and cranny of our plantent from several miles down in the rock to the driest deserts, hot springs, even in ice several degrees below freezing) And cancer is essentially your own cells using this process against you. It can nevertheless be beaten (the earlier the easier and more likely). But the key to success is usually understanding the nature of what you are dealing with.
BOTTOM LINE (IMHO) zinc fingers have the potential to provide some immensely powerful tools*1 to use against cancer. But success will in most cases be a matter of using the right combination of tools for an individuals cancer (as determined by accurate diagnostic tests).
*1 I don't like the meatophor of "weapon" because it implies a war and the "battlefield" is your own body. Wars involve a huge amount of collateral damage which is something that cancer therapies now have the potential to move away from. "Tools" because we should be working WITH our bodies, not against them.