updated guide required for rooting

[orangzeb]

Hola amigos. Long time no see, eh?

Okay I just purchased a used z3 with :
Android 6.0.1
D6603
23.5.A.1.291
Bootloader can be unlocked : Yes

I searched xda and found kingroot method but didn't try it yet as I don't wanna risk anything here. so I'll be thankful if someone tells me about best and stable
1. root method
2. easy unlock bootloader link
3. best recovery guide link
4. A Custom or stock rom either on 6.0 or 7.0 which has best bettery no bugs (possible builtin call recorder? okay if not)

Thanks again.