[Serie: All About Japanese Particles]
Note: Zo adds force to a sentence in a more emphatic manner than ze (#66). Used mostly by men.
1. Indicates a command or threat.
そろそろ会議を始めるぞ。
Sorosoro kaigi o hajimeru zo.
Let’s get the meeting under way.
今度そんなことしたら、絶対に許さないぞ。
Kondo sonna koto o shitara, zettai ni yurusanai zo.
If you do that again, I’m not going to let you get away with it. / If you do anything like that again, you’re going to pay for it.
2. Adds force to words of self-encouragement or self-urging.
頑張るぞ。
Ganbaru zo.
I can do it!/ Make way. Here I come.
今度こそ成功するぞ。
Kondo koso seikō suru zo.
I’m going to make it this time./ This time I’m coming up a winner.
– Source: All about particles – A handbook of Japanese function words –