I've got more or less the same setup (E-PL5, Z-240, D-2000). There are two possible options for you on the Inon strobes. Well, three:
0) Shoot manual
1) Use the E-TTL in which the strobe itself does the exposure. I've never tried this
2) See if, using the right setting of the magnet switch, you can boost the power of the pre-flash so that the main flash does not suck much out of the camera (this means setting the camera and strobe to TTL)
2) is incompatible with 0) which is why I don't use it.
BTW, you're not going to reduce "shutter lag" per se, but you can get the camera to fire more frequently with the 1/64th setting. However, you'd probably still end up with 2/3 of the frames dark since the external strobe won't be able to cycle as fast as the camera strobe (unless you are using very little power).
- Timz likes this