Mixed anova (1 within and 3 between)

I have run a mixed anova with 1 within variable (2 level) and 3 between variables (one with 2 levels, another with 3 levels, and a last one with 3 levels).

It yields a significant four way interaction. And can I decompose and probe this interaction?

Can I combine all the the between variable in order to form a new between variable with 18 levels (2 * 3* 3). Then, I could just re-run the anova for each level of this new variable?

Is it the good way of probing the interaction?

Thanks in advance!