The folks over at iFixit have provided a handy teardown guide for the Sony Xperia Z5. To be clear, the guide is a member-contributed one, rather than from iFixit staff but it very clearly shows the step-by-step process involved in taking apart your Xperia Z5. If you have seen previous disassembly guides for the Xperia Z series, then you will know that removing the back cover involves heating the rear to soften the glue and using a suction cup to prise open the cover.
The teardown confirms the dual heat pipes used in the Xperia Z5. There is also an accompanying video that goes through screen replacement as well as how to fix the charging port and replace battery. Check the full guide at the source link below.