Learn English – “Time zone” vs. “Timezone”

This seems like a good one for Ngram.

It looks like in British English moustache has always been the preferred spelling.

In American English, it's been more of a battle with mustache now in the lead.

So here's a combined view. Both are contenders in the English-speaking world, but clear preferences exist on opposite sides of the pond.

(Have to wonder if the peaks and valleys correspond to mustaches going in and out of vogue.)

Very nice! Methinks you have unearthed a compound word in the making.

I did a narrowly-focused (1995-2005) Google lit search for both time point and timepoint, and learned both terms seem to be found most often in technical writing − often describing scientific, statistically-driven experiments.

The two-word time point is running far ahead of the one-word timepoint (by a ratio of about 10-to-1, at this point in time, at least). However, who am I to argue with the likes of Campbell and Heyer, genome researchers who wrote:

Three microarray hybridizations were carried out for each timepoint.

I don't know anything about microarray hybridizations; I'm not going to intervene as their grammar police.

The main problem with your style checkers is not that they disagree; rather, they should allow both as admissable forms.