Yes, it is possible if the Ralts has a high attack EV, and a good attack nature. The Zigzagoon also has to have a low defense EV and a bad defensive EV. Ralts also has to use Confusion twice if I'm correct instead of Growl, and Zigzagoon basically dies. What happens next depends. If it's randomized, I've heard that a "Bad Egg" Pokemon is created, and luckily for that person, the randomized Ralts had explode, so the run survived. If it's non hacked, non randomized, you white out, but as soon as that happens, the game resumes as if Wally caught the Pokemon. Surprisingly, the exact opposite happened to me in a run of Theta Emerald. Zigzagoon defeating Ralts triggered the latter of the options to me, and hilarity ensues as a friend and I keeled over imagining using Ralts as a last resort meat shield. Boy, my friend and I are morbid. I found this while researching the topic.
According to Bulbapedia:
"This rare occurrence can only happen if Zigzagoon is generated with 11 Attack, and the wild Ralts has a Nature that lowers Defense, an IV of 3 or less in HP, and 5 or less in Defense. With all this, Zigzagoon can do a maximum of 10 damage with its first Tackle, and after Growl is used on it, 7 with its second. This makes for a total of 17 damage, just enough to knock out Ralts. However, the game continues on as if it had been caught. The probability of this occurring is (182/800)(4/25)(4/32)(6/32)(5/16)*(7/16), or about 1 in 8574."
I bet that about the same chances are for the opposite. Hope this helped you!
