To make things a bit simpler, let’s just focus on the two major types of Chinese zha jiang mian (or ZJM). There’s the traditional Mainland Chinese type (to include those iterations from Beijing, Tianjin, Shandong, etc.), and then there’s the evolved Taiwanese iteration.
The major difference between Chinese and Taiwanese versions is the type of fermented bean sauce used. Chinese versions use soybean paste, and the Taiwanese versions generally use sweet black bean paste (oftentimes with a hefty dose of Hoisin sauce, although some Chinese iterations also use a Hoisin blend but it’s less common).
So with all that said, some good options for the Chinese iteration of ZJM, one might try LaoXi Noodle House, Malan Noodles (which may or may not be affiliated with the eponymous chain in China), and Tianjin Bistro.
For the Taiwanese kind, try Cindy’s Kitchen, Pine & Crane, Q Noodle House and maybe Flavor Garden (though haven’t tried it since the shakeup in the kitchen). Places like 101, Liang’s and Mama’s Lu are safe, if uninspiring, bets.
Probably a few other places worth mentioning, but perhaps some other time. And place.