Zoom MS-70CDR+

With its stereo inputs and outputs, this zoom pedal is perfect for synths.
The effects are very good and true stereo in and out.
Perfect for chorus, reverbs, delays, compression... it only lacks distortion!
The fact that you can stack up to 6 effects makes it extremely flexible and useful. (although the interface is a little confusing at first, so read the manual. It's still miles ahead in ease of use compared to more complex pedals like the Hotone Ampero though.)
At this price, it's a must have for synth users, honestly.
A real shame it doesn't include a single distortion or saturation effect though! They clearly want you to buy the other pedal for that.
Shame on you ZOOM!
The pedal will get hacked eventually though, but who knows when...