Z in and X Time base out are useful for various things.
But the /|/|/| ( X out), Z and Y is a blank plate.
Eventually I found a Spanish version of service manual that showed the Z in (TTL blanking 0V = off, > +1.8V = on, not analogue, I tested with a ramp) is simply a pin on the Timebase PCB already (on slightly different versions it's extra transistor and resistors).
There is also a Test multiway connector also on Timebase PCB, which has Sweep out via a resistor.
There were two holes on chassis I mounted pillars on and then put a plate with 3 holes for BNC on the pillars. Very short length of wire for X out and Z in. I didn't figure anywhere handy for the Y, but that's not so important.
Front Panel Y2 is of course switchable to be X in.
If anyone is needing the info I can post the photos. The Spanish manual is on the Hameg site. A third party site with english version doesn't show the Z connection on my Timebase board. The Hameg site English and German versions of 203-6 Manual omit the circuit diagrams!
Now I can drive a VCO or varicap tuner from the X timebase (about 5.5V peak).
Or use a trace Multiplexer
Or a Vector Clock display
I may add Analogue Z in later on the Empty "Y" socket. I don't need a DC-20MHz amp with attenuator.