Can someone help me out with Z88dk?

The z88dk project's wiki has a page that specifically talks about generic z80 code generation starting at address 0. Here's a link to it: https://github.com/z88dk/z88dk/wiki/NewLib--Platform--Embedded. z88dk contains two different compilers and two standard clibs. sccz80 is their original C compiler which can compile more obscure edge cases of the language. zsdcc is a version of sdcc modified to work with z88dk's libraries which can make slightly faster code and has options for using different registers but has fewer features. As for the clibs, the classic lib is the original one that covers many different z80 based platforms but involves more adhoc functions written in assembly. Newlib as the name suggests is newer and more of it is written in C itself with the aim to be more conformant to the C11 standard, but it only supports a few different platforms. One of which is for non system specific z80 output though. A lot of the improvements of newlib have also now been merged back into the classic clib.