Plugging external effects on zed-420

Hello to all,can someone explain to me how to plug external effects on the zed-420.Where in the heck do I plug the return… ???

Thanks !!

You’ve got 4 sets of stereo inputs, just return through any of those (if you’re not using balanced equipment you can use the RCAs, or run balanced into the TRS jacks)

iDR32 mixrack

MixRack for iPad & Tweak for iPhone apps

Asus N61 Laptop (x2 wireless)

Sennheiser IEM (for PFL)

Dante card (soon!)

But of course !!!,thank you so much !