A key thing to keep in mind about zagara is that she isn’t a mage, and she isn’t a “marksman”, she’s a summoner. Her aa damage isn’t going to beat out aa-based heroes, and her ability damage isn’t going to beat out casters, so what makes her work is being able to align her attacks with her summons. If zag doesn’t attack with her summons, then they can easily be killed, and she gets chased off; if she doesn’t hide behind her summons, then she can’t really trade hits against anything, and she gets chased off.
A key trick to zag is taking the right talents for how you’re going to use her summons, In QM players may try to constantly split-push, avoid team fights, and think they’re going to win the game alone by being persistent and ‘sneak’ structures down. That might hold up for murky tactics since he trades up, but it doesn’t work well for zagara.
Nydus zag can split and be there for team fights, so choosing one over the other is undercutting her ability to pressure backline heroes with a flanking hydralisk, or screen skill shots with roaches. Maw zag, on the other hand, can cluster enemies if allies have follow-up wombo, or can stop otherwise unstoppable enemies and be used as a counter/stall. Nydus cdr is useful if players are attacking to then be able to get out more summons (for % damage late) and Maw is handy as a stall-to-escape if you’re against select gankers, so either heroic isn’t necessarily the ‘go to’ build for her.
Creep control and summon placements are the big things that set apart zagara. Creep gives vision and a ‘zone’ of control where zag gets extra attack range and speed that allows her to poke or aggressively position behind her summons. Summons aren’t just mindless spells to cast either; when and how they’re placed makes a key difference on them taking damage for lane minions (summons have limited time, so any damage they can take can help a lane push) or not getting killed early so they can continue to deal damage to enemy heroes.
When pushing, roaches should land on the ranged minions to both draw some attacks from them while also dealing damage to the easier to kill units. Hydralisk should usually come after roaches so pve/hero damage hits them and gives the hydra more time to deal damage. Hydra’s should also avoid being cast at their max range as time they spend moving is time they don’t spend attacking – which also holds true for enemy heroes; if they are compelled to run (Taking damage from zag and summons) then that’s time they usually aren’t attacking back.
One particular flaw that gets overlooked with zag is how long it takes for her to turn around. Compared to other heroes, zag actually has to rotate around which way she’s facing, so back-and-forth clicking can slow her down and take time away that could be used to reposition for attacking, avoiding enemy skills, or even running away. Practicing stuttering or ‘orb walking’ (using spells instead of basic attacks, such as with timely Q casting) can help be more particular on how you click and move with zagara to minimize time lost to turning.
Q talents have arguably been overnerfed, so roach/hydra talents are usually the go to for pushing lanes and dealing pve damage. Her aa-quest is more of trap talent (takes too many stacks for too little reward) but Medusa Blades + lvl 16 aa boost is better than I think people are willing to consider cuz… % damage. Similarly, mutalisk is underrated imo as people neglect how much damage they can end up dealing due to splashing attacks and having more than one alive during objectives/fights/etc, esp with the lvl 20 hydra talent.
The trickiest part of Zag is that she was mostly an early-game hero that had a lot of her early game cut out and repositioned for the late game. Aggressive and experienced players can force an early xp lead, but functionally, it’s usually ‘better’ to play it safe with her and try to stall for the later game where damage from her summons can eventually overwhelm most of the enemy team provided they can’t/don’t dive on her hard.