Thanks to you both for the information you provided and for your suggestions. I'm a little sentimental about my K, and I want to fix it right. So I am still looking for the missing wire.
I know from the attached photo, which (I captured from a U-Tube video) and from the wire and connector remnants I found underneath my ZG123S-48 that there were two wires from the wiring harness running into the PTO clutch connector and two wires running to the PTO clutch from of the other side of the connector. As previously noted, one of the wires from the wiring harness was green/yellow, and the broken end of that wire is visible coming out of the wiring harness near the starter solenoid. Based on the photo and wire remnants, the other wire appears to have been a bluish color with a red stripe. The wire remnant that is still attached to the chewed=up connector is five or so inches long, possibly indicating that the break has to be somewhere close to where the connector was located near the starter solenoid. But I simply cannot find it. The color code appears to be the same as the two wires connected to the starter solenoid, and I thought that there might have been two wires in one of the starter solenoid terminals, but I cannot see any evidence that the wire that was pulled away came from there.
I have new wires spliced onto the PTO clutch and am now waiting for a shop manual I've ordered to come in the mail.
Lugbolt, FWIW, the dealer that I bought the mower from installed the brake switch kit a while back. He told me it was quite a task.
Thank y'all again.......
PS: The photo is from a U-Tube video referenced earlier in this thread. So please ignore the captioning on the photo.