Oops, I wasn't familiar with the Zeibeck so I took a guess. I'm not sure I would move it from where I suggested, maybe a little later in the chain, but I don't think it's location in the chain will have a big impact on how it sounds. I would still put the Ampeg later in the chain and the MarkBass early, but there are widely varying opinions about this and it's subjective.
There are a lot of different octave pedals, and they sound different and have different capabilities, so this is a case where you should try some (or listen to YouTube demos) and see what you like. The big decisions are analog vs. digital and whether you need an octave up or a sub-octave or just a lower octave. I somehow ended up with five. I probably use three regularly. EHX Nano POG (digital, low and high octaves), Boss OC-2 (analog, low and sub only), and 3Leaf Octabvre (analog, low and sub only).