When the Sennheiser TRRS connector is wired properly in the cable (so each connector pin their own wire) it is just a matter of correctly soldering the individual wires to the XLR-4 plug.
You cannot do this when, for some cost saving or ignorant reason, the cable itself is 3-wire.
Still... there are some amps with an XLR-4 output just for convenience. These have the pin 2 and 4 in the XLR plug tied to ground.
The HD560S can be used balanced (with the right cable) and SE (with the right cable).
You can also cut the 6.3mm connector from the original cable and solder an XLR-4 connector to it. The Sennheiser cable is 4-wire internally.
My post does not need correcting. I merely stated how a correctly made balanced cable should measure.