From what I can see of those sound effects:
The second-to-last panel is "Zaan." It can be a slash, but it can also be a tumbling and falling sound. The "a" is elongated, indicating a slight drawing out of the sound. I'm guessing a slightly slower fall, like slow motion.
The last panel is "kikiki" which is a screech or a squeal, like tires on a pavement trying to stop and losing traction. It's also used as an evil laugh, or a bat cry in some contexts I've seen.
What the actual meaning of these sound effects are -- a native could probably understand their context better -- will be revealed next chapter. Or in the spoiler tags people have left.