2 track using 072 and 60 curves on an 8x8' layout

I think it can be done.  But the result will be two concentric circles with VERY short straightaways, where the crossovers between loops would go.

Do your trains NEED broad curves like O60 and O72?  If all you have is 8x8, you would be so much better off going with "traditional size" trains on O31 or perhaps O36 curves.  I recently shared my thoughts about this on another post... Ted's thoughts about wide curves in a small space

You didn’t specify what type of track you are planning on using… I use Lionel Fastrack. The pic below shows one of my crossovers. The outside track uses O-84 and the inside O-72. The four switches are all O-72. As long as the connection is on a sufficiently long straight section, it shouldn’t be too difficult to set up. If you wish, you can easily isolate the two loops. Hope this helps.

One more thing… if you plan on using Fastrack, Lionel used to put out a special Track & Power catalog. Here is a link to the last one they did in 2016/17. Page 19 has a number of examples of crossovers with the required pieces of track.

http://catalogs.lionel.com/16tp/html5/

You don't have long enough straight sections to make "standard" crossovers, so here's a way to do it by placing 2 O-60 FasTrack switches on inner O60 curves and O-72 switches on outer straights. The O-60 switches need the 1 3/8" half roadbed pieces that come with the switches. O-60 switches could be used in place of the the O-72 switches, but then you'd need to use the half roadbed pieces and adjust the ovals. It's just easier to use the O-72 switches and avoid that. The blue track center rails are approximately 3" from the edges. Center to center spacing between the ovals is over 5".

My present layout is 8x9, I decided to go to a single track design with Atlas 063 curves. I have done this to make room for scenery instead. Although having room for larger equipment that requires larger curves is great, all you wind up with is 2 loops with very little straight sections.