Zypper is a command line tool for package management, it's based on ZYpp, aka libzypp.
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Zypper uses a SAT solver for dependency solving issues and this helps with increasing Zypper's speed considerably.
Pro Great dependency solver
Zypper's dependency solver is built on top of SAT solver which is one of the best package dependency solvers available for Linux.
Pro Clean and logical
Pro Delta rpms
Pro Beautiful and powerful GUI
YaST2, the GUI for Zypper, is very powerful and elegant. It's very fast and responsive, it features an excellent UI and very intuitive repository management, and it can be configured to run using GTK+ or Qt5.
Con Manual conflict resolution required
Every single time a package trying to be installed or upgraded has a conflict, Zypper asks you what to do. There is no way to automatically just upgrade packages that will upgrade without any problems.
Con Not the default package manager for many systems
Zypper is still relatively new. As such, it's not available as the default package manager in many systems.