Hi$,$ while I$\text{'}$m solving this problem, I got:

What is the weakest precondition for the entire code $($aka$,$location L$1)?$ z$==0$&&x$<0||$z$!=0$&&x$>0$or$($z$!=0^($x$>0$&&y$==0)$vFalse

What is the weakest precondition for the entire code $($aka$,$location L$2)?$ z$!=$&&x$>=-2$&&y$==0||$false

What is the weakest precondition for the code at location L$3?$ false

What is the weakest precondition for the code at location L$4?$ x$>0$&&y$==0$

Please double check your answer.