Activate Zameck Guildmage's first ability by paying ({G} magic symbol) ({U} magic symbol) , causing each creature you control to enter the battlefield with an additional +1/+1 counter this turn.
Activate Phyrexian Altar by sacrificing Glen Elendra Archmage, adding one mana of any color.
When Glen Elendra Archmage dies, it triggers its persist ability, returning it from your graveyard to the battlefield with a -1/-1 counter and a +1/+1 counter on it.
The two counters are removed from Glen Elendra as a state-based action.
Repeat from step 2 any number of times.
Once you have infinite mana, you amy activate Zameck Guildmage's abilities any number of times.
Results
Infinite +1/+1 counters on Glen Elendra Archmage and on creatures that enter the battlefield under your control this turn.