Given MTOM=230, AZFM=MZFM=173 and Fuel on board = 45, the following applies:
AZFM=<MZFM, ie. this is ok.
ATOM=173+45=118
ATOM<MTOM, ie this is ok.
So you could go.
(What you have to consider is the most limiting weight; stuctural take-off mass, performance limited takeoff mass (could be runway, climb or obstable limited), zero fuel mass and landing mass (again either structural or performance limited), and of the three, the most limiting will be your limit.
In plain text in your example, you could go, and you could add weight, however, all weight above MZFM must be fuel, so you could fuel up, but not add cargo etc. This is all based on there not being any performance limiting factors.