It's because you have the wrong font package. You must use "Zawgyi iOS 4.3 font"
You must remove your current zawgyi font and install "Zawgyi iOS 4.3 font"
1: Firstly, you cannot remove zawgyi font directly. You need to install "Zawgyi Font iOS Uninstaller" first. This step is really important, otherwise you might end up restoring your device.
After installing uninstaller, remove zawgyi font.
2: After removing, install "Zawgyi iOS 4.3 Font".
NOTE: I don't expect any issues, but I am not responsible if anything happens.