This is what I do for my tool bag. I also leave a note inside with a couple more zip ties taped to it, asking whoever is going through my stuff to please zip it again. Somewhere near 80,000 miles traveled this year and it seems like a decent solution.
These can be quickly opened with a narrow flat screwdriver.
But they probably wouldn't bother with it in practice.
The goal is not to secure the luggage; its used as tamper evidence.
The point being, once opened non-destructively (with a screwdriver), cable ties are easily re-closed, leaving no trace of tampering.