You will struggle to get access to the front two from the top even from underneath access limited.
The rear two are not the most simple either as all on the top side of the pipework
If you haven't got any pictures by the weekend I'll send you some ( just won't be able to get my zed on a ramp before then )
Why are you needing to change all 4 lambda sensors as generally pretty reliable on the 2.8 engine.
Stephen.