There are actually many wide and varied eyepieces that fit the Pentax. It will accept any astronomical 1 1/4" eyepiece. This includes Pentax's awesome XW fixed power eyepieces, Nagler astro eyepieces, Baader Planetarium, etc. That is a great feature on its own.
I had the most common eyepiece packaged with the Pentax 65: the XF SMC 20-60 designed for the 65. The physically bigger, more expensive XW SMC Zoom is a 20-60 on the 80mm pentax (the body it was designed for), but roughly a 15-45 power on the 65. This makes it a similar performer to the Zeiss 65. I haven't seen the XW zoom as a scope/eyepiece in a discounted package with the 65, and I never actually looked through that eyepiece on my 65. There are many third party zoom and fixed eyepieces that can be used with the Pentax. It is very versatile.
The optical performance of the Pentax was pretty darn good with the eyepiece I had. It did get dim in higher powers. The biggest issue i had was durability. I had mine in its included cordura case, wrapped in a fleece jacket and packed away in my Eberlestock backpack for a 3 mile hike to a glassing spot. When I got there I pulled out the scope and WHOA! the scope body had broken completely. Now I didn't fall or even rest against a tree with my pack. Pentax honored the warranty (cost me the worry-free fee of $20) and replaced the scope, but I just put it straight on ebay for a birder to use, because I must have confidence in my gear. Maybe it was just my particular scope, but why risk it when bucks and bulls are at stake!
Enter the Diascope 65, which in my opinion is better in every way, especially the robust build of the scope.
My diascope is a fine optical instrument that also happens to be really tough. It resolves more detail at 45 power than my Pentax did at 60. Check it out ... put it right next to the Pentax and Swaro HD ... I did. Put a credit card on a fencepost 80 yards away and check resolution. I bet you will be astounded. I much prefer the dual focus rate feature on the Zeiss to the Swaro full-ring focus style.
The thing is there is some particular unit-to-unit variation with all brands of spotting scopes. Maybe I had a great Zeiss when I compared it to a not-so-great Swaro. Maybe I would see something different if I got two different units. The point to my posts, if I can get to it without rambling any further, is the Diascopes ARE comparable to the Swaro and others. I suggest you compare them before you choose.
I am keeping my Zeiss.
Enjoy whatever you choose to get.