This is a high level explanation of the basic idea:
In The basic zone blocking for a run, each lineman blocks every defender that appears in front of him. An o-lineman has no predetermined defender to block, it is whoever shows up in front of him after the snap (obvious exception: if a d-lineman is in front of you, you block him). At the snap, the o-line continuously moves to the playside, blocking any defender that appears. The backside linemen may be assigned specific backside linemen to block (e.g., the DE and DT).
The running back reads the blocks. The running back is looking for a gap with no defender and then runs through the gap. The back initially runs with the o-line, but has freedom to cut back if he sees an opening.
In the basic zone read option, the o-line leaves a backside player unblocked for the QB to option.
In basic triple option blocking, each lineman has a dedicated defender to block. The lineman has to identify, pre-snap, which defender he is responsible for and then go block that defender at the snap. The defender to be blocked isn't a specific player in so much as it is a player in a specific spot relative to the other defenders. For example, an o-lineman might be assigned to block the the first player inside the pitch key. That player could be a linebacker, it could be a safety. This is partly why defenses shift pre snap. It forces the lineman to re-determine which defender he is responsible for. For example, the lineman might now block the DT and someone else now has responsibility for the first player inside the pitch key.
The running back simply runs his assigned track and waits for the ball to be given to him (or not).
I don't have an opinion about which scheme is more difficult to do. The zone blocking is more difficult than it sounds.
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