@steve
An insert cable like the one shown has a single TRS (Tip/Ring/Sleeve) jack at one end, with one ground connection, one send connection and one return connection.
At the other end there are two jacks, one for send and one for return.
So the insert sockets on ZED’s (and most mixers), including the ZED10FX are like an output and an input socket in one.
The cables are quite common, though not always labelled as insert cables, often as 1x stereo 1/4″ jack to 2x mono 1/4″ jacks
It’s the Tip which is the send and the Ring which is the return, so if you do get a cable that’s usually used for stereo jack to mono Left and Right Jacks, it’s the left jack that’s the send which should go to the input of external equipment and the right jack which is the return and should be connected to the output of external equipment.
Note that the signal is unbalanced.
Hope this helps!
Keith.