Looks like same shell/casing, but different internals. Romisen RC-C8 has Q5 emitter whereas the Z3 has the XM-L T6 etc. Or perhaps thats what you meant? :)
I have noticed that my Trustfire Z3 seems to require a flat-top battery (like AW 2900 mWh 18650) to work well. The button top batteries don't seem to make a good connection.
The Romisen RC-C8 is a good little zoomie flashlight. The minor problem is that it's one-mode: on. Well, two modes if you count OFF.
The major problem with the RC-C8 is that it uses a CR123A battery, which is a weak power supply. It runs the flashlight for 20 minutes or so, then suddenly turns itself off because the battery voltage has fallen to 2.8V and needs to be charged back up to 4.2V with one of those cheapo Chinese plug-in wall chargers.
Totally different light. 
I do like the clip option though.
@Jenab6:
"The Romisen RC-C8 is a good little zoomie flashlight. The minor problem is that it's one-mode: on. Well, two modes if you count OFF."
Now I'm really puzzled 
. This is the spec as listed by DX; multi-mode and three different battery configurations (though it wouldn't be the first time DX listed faulty info) Did Romisen make different versions of this light?
| Brand: | Romisen |
| Model: | RC-C8 |
| Casing Color: | Black |
| Emitter Brand/Type: | Cree |
| Emitter BIN: | Q5-WC |
| Color BIN: | White |
| Total Emitters: | 1 |
| Battery Configurations: | 1*18650/2*CR123A/3*AAA battery (Batteries not included. Battery adapter included) |
| Voltage Input: | 3.0~8.0V |
| Switch Type: | Clicky (Clickie) |
| Switch Location: | Tail-cap |
| Modes: | 3 |
| Mode Memory: | - |
| Mode Arrangement: | Hi > Mid > Fast Strobe |
| Circuitry: | Digital Regulated 800mA Current Output |
| Brightness: | 210 lumens maximum brightness (manufacturer rated) |
| Runtime: | 40 minutes (manufacturer rated) |
| Lens: | Plastic Convex Lens |
| Reflector: | Plastic Smooth Reflector |
| Special Features: | Slide the bezel to change beam pattern between flood and throw. Twist the bezel out for rectangle, Twist the bezel in for circular |
| Strap: | Included |
When is a zoom light most useful?
To me, the whole purpose of a zoomie is to have something that you can have with you, when you don't expect to need a flashlight. If you don't expect to need a flashlight, how can you possibly know if you will want a flood or a spot, should you find that you require a flashlight?
I was out walking the other evening and I was using my Redline zoomie on low power, in flood mode, just to illuminate the path in front of me. I decided to take a shortcut across the golf course, to get home and about half way across, I saw some movement out of the corner of my eye. I twisted the light to full zoom, switched it to high power and pointed it in the direction of the motion, just in time to see three deer crossing the golf course. When the beam hit them, two of them stopped and looked at the light. I was glad that I had a zoomie.
BTW, it's also a zoomie that can fit in my pocket. I'm replacing it with a T/F Z3 (about the same size), as soon as the new one comes in from China.
I have one right here. It turns on. It turns off. Nice. But it's only one mode. Either the ad is wrong or there's more than one kind of RC-C8.
Ah, I see! That last post is your first mention of Romisen RC-C6; previously you've been referring to it as 'RC-C8'. Two completely different lights. Puzzle solved.. 
Those are different lights that Romisen makes (of many more)
and also, Shiningbeam.com has custom models (brighter emitter and different driver) for a lot of the Romisen lights
So it's easy to get confused if that's not specified clearly.
Yes, that pesky teeny tiny lettering on the flashlight is hard for me to read.
For those interested in the Trustfire Z3, I’ve written a review on it. 
” https://budgetlightforum.com/t/-/14351”:https://budgetlightforum.com/t/-/14351