I do know
haha
To do it i'll recomend you to use Notepad++, because it reads plenty of formats
Well you'll have to edit the file called common.ini (inside the skin)
[Font_Softkeyse](name of the line to edit)
The exact number is this:
Size=20
You'll have to play with numbers to see how big or how small you want it
That will be one part
The other file to edit is the phone.ini
You'll have to edit the line named [idle padding_bottom]
There you edit the value
Padding_Bottom=60
to the value you may like
Then you'll need to edit
[ZSoftKey_left]
and
[ZSoftKey_right]
Playing with this values will give you a bigger or smaller softkey font (actually it'll make the bottom bar smaller, which will reduce the font size )
You'll need to change two values Padding_Top and Bottom, reduce them give allow you smaller fonts
You need to do it in both left and right SoftKeys otherwise it'll look odd Further reading(It's in kinda spanish/portuguese languaje)
Well i do know some values but you need to try it yourself otherwise you might end with something you don't like, you should try over and over again, as i don't have a Z6 the value i give you might not look good on your screen