"This one is just guitar and vocals, and there's an honest, singer-songwriter buzz going on.
"It's pretty vulnerable. We've been shaping it for a while, and I've been trying to get my pipes [voice] up to scratch."
The pair shot a music video for the song at Mt Ruapehu with Whanganui film-maker Joshua Dey.
"It was really fun going up there, but while we were shooting, Andrew started having all these tummy cramps," Isaac said.
"We were joking around, saying his appendix was going to blow up, but later that night he actually got rushed to hospital.
"They took his appendix out straight away."
Isaac said the song itself has a more personal feel than previous Something Zesty releases.
It had been in his song bank for a while, but getting his vocals up to standard meant he could finally do it justice.
"I was in a place where I was quite kind of stuck by myself, with a few things going on behind the scenes.
"You kind of know something is going nowhere, but you try and hold on to it for as long as you can.
"It's not just a song about a girl, though; it's written from quite a distant perspective. It can be applicable to a lot of different situations, I think."
As well as the new single, Something Zesty is well into season two of Speed Cooking, an online video series where the pair compose, record and release a new song in a matter of hours.
Isaac says it's been liberating to work on music without the confines of a full-band setup.
"Being in a band can drive you bonkers sometimes.
"I'm really excited about the Zest. There's some funk songs, some punk songs, and some of this more serious stuff as well.
"There's a whole world shaping up, which is all looking pretty cool."
The duo have now become a trio, with Ethan Coleman (Drxnes) joining on drums.
They will be taking the stage at next year's Sound Valley music festival at Oceanview Speedway, and Isaac said Coleman's beats are bound to add a weight to their sound.
"Doing live shows will validate the Zest a bit more I think," Isaac said.
"It's game on."
Footprintz will be available on all major streaming platforms from November 4.