The description on the Celestron site mentions their binoviewer is suitable for telescopes with at least 3.5” back focus. They also mention the unit may not come into focus with Newtonians. This to me indicates the binoviewer is 1x since 2x is typically needed to use with Newtonians.
The clear aperture of the binoviewer is listed as 22mm. I would think a pair of 20mm Superview (68deg) would be a very nice low power pair with greater true field than a pair if 25mm Plossl. A pair of 15mm Superview would be a very nice slightly higher power pair for the Moon. Combined with a 2x Barlow you can then also have 10mm (20mm + Barlow) and 7.5mm (15mm + Barlow). This is all you would ever need and all options would give 68 deg apparent field. Bintel has these for $59.00 each.
The zoom is handy to determine what fixed focal length eyepiece would give the best magnification for a particular target. I have the Tele Vue click-stop 8-24mm zooms but I also have a pair of 24mm Panoptic, 19mm Panoptic and 16mm Nagler. (Looking for another 15mm Panoptic to give me a bino pair as I really like the 68 deg field). The 82 deg field of the Nagler is very nice though when binoviewed.
The zoom has a varying apparent field and in the case of the Baader it varies from 48 deg at 24mm to 68 deg at 8mm. Whilst this seems counter intuitive it is like this so the true field remains relatively constant (or close to it particularly between 16 and 8mm).
See
https://www.baader-planetarium.com/e...om_mark_iv.pdf