Colwyn Bay progressed as expected through goals from Aaron Williams, Jordan Davies (pen), Louis Robles, Jamie Cumming and super sub Max McGoona.
Match report appears elsewhere on Grassroots North Wales.
This all-Cymru North tie saw Llandudno progress without too many alarms.
The Seasiders took a 17th minute lead when Callum Stephens headed home from a Ben Maher corner.
Mountain hit the bar soon after, but it remained 1-0 at half time, Mark Cadwallader going close just before the break after rounding keeper Stephen Bullen.
Tudno went two-up on the hour when great work down the left by Adam Stephens resulted in sub Harvey Bennett knocking in his eighth goal of the season.
Bennett then turned provider for fellow substitute Kieran Smith to make it 3-0 on 70 with his second goal of the campaign.
An Arwyn Parry Jones double, plus further goals from Aron Roberts and Nigerian Albert Nosakhare secured maximum points for an impressive Llanystumdwy.
All four goals came within the first hour with the hosts taking a commanding 3-0 lead into the break.
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