The ZX BASIC SDK
As you might already know, ZX BASIC is not a single program. It consist in 3 python (.py) programs that might be used standalone or not, depending on how they are invoked.
ZXb is the main compiler executable (for Windows you can use the .exe converted version). It will compile a BASIC program into a binary file. At this moment, supported binary formats are: TZX, TAP and raw binary (.BIN) format.
Go to the zxb page for help on using the compiler.
ZXbasm is a cross-platform Z80 assembler. It will assemble plain ASCII files containing asm source code into the same formats described above. This tool is completely finished.
Go to the zxbasm page for help on using the assembler.
The zxbpp utility is a preprocessor which works in the same way as many C preprocessors (cpp) programs do. It is used both by zxb and zxbasm. It basically filter an input file and produces a modified output one, by replacing macros and include files. If your used to C preprocessors (e.g. you've used Z88Dk), you will probably be very familiar with it.
Go to the zxbpp page for help on using the preprocessor.