It's not that I mind Zanka having a type, or focusing on a single topic. All their work and art can be about maids, sure, that's no problem. Make a million different maid manga, hell yea that slaps. Nagori Yu is one of my favorite artists, and they have a one track mind too (small young girl and big scary older woman)
The problem is when Zanka keeps one of the series going, it just feels like the same 5 pages over and over. Nothing seems to really change. It even explains to us the premise every single time.