I've owned and used both of those scopes. Optically the Zeiss is better, especially in it's ability to resolve detail. I also think the etched reticles Zeiss uses are better than the wire reticles Leupold uses. They're just the right thickness for me and appear sharper and crisper. I've never had a problem with either a Zeiss or Leupold in terms of durability. The only time I've ever had to return a scope for service was when I dropped one of my rifles onto a paved parking lot which damaged the 4.5-14x44 Conquest on it. Zeiss replaced it with a brand new one within a week, free of charge and no questions asked.

So if it were me I'd go with the Zeiss Conquest unless it interferes with the operation of your rifles's bolt. I oncehad a Conquest on my pre-'64 Model 70, but its larger ocular bell caused clearance problems when Icycled the bolt. I ended up putting a Leupold VX-II on it because of its smaller eyepiece.