Verified answer

ここぞというとき = when it counts, when it's really important.

Literally: "when you say 'this is the time'".

As you may be aware ここ basically means "here", but it very often means "now" too, which is the case for this phrase.

-ぞ is a sentence-ending particle of Classical Japanese indicating emphasis. It can be paraphrased as ここだというとき in Modern Japanese, but we usually use it in the Classical style.

ここぞというとき

koko= here

zo= sentence's end, mainly masc., add force.

toiu= said, called thus

toki= time, when etc...

so I think literally "here! The so called time". But you need to figure out from the context.

I think it means "when it comes to the crunch." I hope this helps :D

It's time now like in "it's time now to go" or "it's time now to do"