Add a letter in the middle of a Text in every Line, Notepad++

I have a huge amount of lines containing this for example this text: OU111_DI_Z006_1

Note that some chars are different in every line, represented by @. Like this: OU@@@_@@_Z0@@__@

How can I use the search replace function to add the char X in between Z and 0?

Like this: OU111_DI_XZ006_1