SUMMARY
When applying an effect zone to the motion tracker effect with blur it takes off the blur and throws the motion tracker shape off its path. The effect zone is also not accurate (the motion tracker shape starts at a different point and ends at a different point than what the effect zone prescribes).
Applying an effect zone to a sandwiched blur effect (using the motion tracker data for an Alpha Shape (Mask) effect) also is not accurate.

STEPS TO REPRODUCE
1.  Open the attached project file
2.  Enable and disable the effect zone in the clips
3.  Watch

OBSERVED RESULT
Without effect zones, the Motion Tracker effect on the first clip, and the sandwiched Blur effect on the second clip work as designed and expected; applying the effect zone changes the effect's start and and points but not as defined by the effect zone. In the case of the Motion Tracker, the blur is gone.

EXPECTED RESULT
The effects work as designed and expected only for the period defined in the effect zone.

SOFTWARE/OS VERSIONS
Kdenlive: 25.04.1
MLT: 7.32.0
FFmpeg
KDE Frameworks: 6.13.0
Qt: Using 6.9.0 and built against 6.9.0
KDE Flatpak runtime (Xcb)
Build ABI: x86_64-little_endian-lp64
Kernel: linux 6.12.10-76061203-generic