Is it possible to switch from Z4 to Z5 while trading live and letting the trades opened by Z4 be continued by Z5. I have read the relevant section in the manual. My understanding is that copy Z4.trd to Z5.trd (assuming that both are compatible strategies) and start trading Z5. Will this work?

Probably not. Z4 and Z5 use the same trade method, but the algorithms are different in some ways. It is better to let Z4 expire and start Z5 separately.