I just sold a Palette 62, and I loved it. Great case. And the limitation drove me to squeeze every drop out of modules.
I’m pretty sure the depth is the same throughout. I have a 2hp play I wish I could test the size for you.
Never had a Zadar, but it does indeed seem like a great module.
The only thing I’m curious about is the clock. Are you planning on modulating it? If not I’d just run off an LFO off your other modules, and I would expand to the 6hp FX Aid as it has more CV and also you CV its sample rate. I run both the 4hp and 6hp versions and the 4hp gets used as set and forget verb cause the knobs are pretty tight. 6hp much more tweakable. Can’t go wrong with either though super sick modules. For either you will have to use a power cable without the clip on the top to make it fit which you can just pull off if needed.
Hope that helps!